Fortunately, I found the great resources available at govtrack very quickly, but even after cursory examination, I realized there were quite a few difficulties. First almost all votes are along party lines. I would therefore not be able to do any simple comparison of the success rates of senators, as those would clearly map to the success rates of their respective parties. Second, very few roll calls relate to bills, as most of them are procedural. Unfortunately, I could not figure out any way to include or exclude a given roll call based on its type or its potential importance that made sense. For all I know, something that looks trivial like a move to table an issue could be very important, while the passage of a bill might have unanimous support and thus be irrelevant to my investigation.
I therefore decided to look at votes by senators when the majority of the senators' fellow party members voted the other way. Roll calls under such conditions become prima facie important, as breaking party lines suggests the potential disruption under which a bellwether senator could be useful.
So here are some tables highlighting the discoveries I have made in the analysis of this question. The date ranges are from 1989 through 2016, as the data from before 1989 is formatted slightly differently and I would need to write more code to handle it.
Notes on column headings:
- All: all of the votes made by this Senator. This value is not used in any subsequent calculation but is offered for scale.
- Total: Number of times the Senator voted against the will of the party.
- Successful: Number of times the Senator voted against the will of the party and the roll call resolved in the manner the Senator voted.
- Success Pct: Number of successful votes against the will of the party divided by all the votes against the will of the party.
- Senator: The name, party, and state of the Senator. If the Senator belonged to more than one party or represented more than one state, all are listed. All votes indicate the party to which the Senator belonged at the time of the vote, and that is the party used to determine if the Senator voted with or against the will of his or her party.
Top 20 Senators with the most votes against their own party: 1989-2015
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 7173 | 1786 | 900 | 0.50 | Arlen Specter (Republican,Democrat - PA) |
| 6089 | 1631 | 1072 | 0.66 | Susan M. Collins (Republican - ME) |
| 5975 | 1532 | 856 | 0.56 | Olympia J. Snowe (Republican - ME) |
| 5818 | 1375 | 671 | 0.49 | James Jeffords (Independent,Republican) - VT |
| 8752 | 1249 | 514 | 0.41 | Richard C. Shelby (Republican,Democrat - AL) |
| 8085 | 1165 | 774 | 0.66 | Max Baucus (Democrat - MT) |
| 7992 | 1139 | 406 | 0.36 | John McCain (Republican - AZ) |
| 6932 | 1098 | 530 | 0.48 | Robert Byrd (Democrat - WV) |
| 5323 | 1083 | 754 | 0.70 | John Breaux (Democrat - LA) |
| 7798 | 994 | 509 | 0.51 | Kent Conrad (Democrat - ND) |
| 6221 | 991 | 222 | 0.22 | Russell Feingold (Democrat - WI) |
| 3752 | 988 | 582 | 0.59 | Ben Nelson (Democrat - NE) |
| 3696 | 966 | 506 | 0.52 | John Chafee (Republican - RI) |
| 7789 | 934 | 575 | 0.62 | Richard G. Lugar (Republican - IN) |
| 5273 | 898 | 400 | 0.45 | Ernest Hollings (Democrat - SC) |
| 7835 | 867 | 404 | 0.47 | Herb Kohl (Democrat - WI) |
| 2682 | 864 | 444 | 0.51 | Mark Hatfield (Republican - OR) |
| 2767 | 835 | 442 | 0.53 | Howell Heflin (Democrat - AL) |
| 8915 | 833 | 346 | 0.42 | Chuck Grassley (Republican - IA) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
Top 20 Senators with the most successful votes against their own party: 1989-2015
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 6089 | 1631 | 1072 | 0.66 | Susan M. Collins (Republican - ME) |
| 7173 | 1786 | 900 | 0.50 | Arlen Specter (Republican,Democrat - PA) |
| 5975 | 1532 | 856 | 0.56 | Olympia J. Snowe (Republican - ME) |
| 8085 | 1165 | 774 | 0.66 | Max Baucus (Democrat - MT) |
| 5323 | 1083 | 754 | 0.70 | John Breaux (Democrat - LA) |
| 5818 | 1375 | 671 | 0.49 | James Jeffords (Independent,Republican) - VT |
| 3972 | 752 | 621 | 0.83 | Lisa Murkowski (Republican - AK) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
| 3752 | 988 | 582 | 0.59 | Ben Nelson (Democrat - NE) |
| 7789 | 934 | 575 | 0.62 | Richard G. Lugar (Republican - IN) |
| 6932 | 1098 | 530 | 0.48 | Robert Byrd (Democrat - WV) |
| 6530 | 761 | 522 | 0.69 | Ted Stevens (Republican - AK) |
| 8752 | 1249 | 514 | 0.41 | Richard C. Shelby (Republican,Democrat - AL) |
| 7798 | 994 | 509 | 0.51 | Kent Conrad (Democrat - ND) |
| 3696 | 966 | 506 | 0.52 | John Chafee (Republican - RI) |
| 8784 | 822 | 491 | 0.60 | Harry Reid (Democrat - NV) |
| 5525 | 660 | 458 | 0.69 | Mary L. Landrieu (Democrat - LA) |
| 7422 | 757 | 452 | 0.60 | Joseph I. Lieberman (Independent,Democrat) - CT |
| 6564 | 734 | 450 | 0.61 | John Warner (Republican - VA) |
| 2682 | 864 | 444 | 0.51 | Mark Hatfield (Republican - OR) |
Top 20 Senators with the highest success rates voting against their own party: 1989-2015
Note: only showing senators with more than 5 votes against their own parties| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 70 | 12 | 12 | 1.00 | Jeff Chiesa (Republican - NJ) |
| 354 | 23 | 20 | 0.87 | Mike Rounds (Republican - SD) |
| 1003 | 49 | 42 | 0.86 | Tim Kaine (Democrat - VA) |
| 1481 | 147 | 126 | 0.86 | John Hoeven (Republican - ND) |
| 3972 | 752 | 621 | 0.83 | Lisa Murkowski (Republican - AK) |
| 761 | 212 | 175 | 0.83 | Scott P. Brown (Republican - MA) |
| 351 | 11 | 9 | 0.82 | Gary Peters (Democrat - MI) |
| 1294 | 116 | 93 | 0.80 | Ken Salazar (Democrat - CO) |
| 1215 | 547 | 431 | 0.79 | Zell Miller (Democrat - GA) |
| 4033 | 432 | 337 | 0.78 | Lamar Alexander (Republican - TN) |
| 354 | 36 | 28 | 0.78 | Shelley Moore Capito (Republican - WV) |
| 415 | 35 | 26 | 0.74 | George LeMieux (Republican - FL) |
| 355 | 19 | 14 | 0.74 | Thom Tillis (Republican - NC) |
| 977 | 150 | 109 | 0.73 | Jeff Flake (Republican - AZ) |
| 1483 | 230 | 167 | 0.73 | Kelly Ayotte (Republican - NH) |
| 1769 | 162 | 117 | 0.72 | Mike Johanns (Republican - NE) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
| 6424 | 598 | 429 | 0.72 | Pete Domenici (Republican - NM) |
| 2356 | 217 | 155 | 0.71 | Roger F. Wicker (Republican - MS) |
| 1207 | 209 | 148 | 0.71 | Mark Kirk (Republican - IL) |
Top 20 Senators with the highest success rates voting against their own party when it counted: 1989-2015
By "when it counted", I mean that these calculations are made in situations that required one or more Senators to vote against his or her own party for the result to have been what it was. For a detailed discussion of what this means, see the Code Book.Note: only showing senators with more than 5 votes against their own parties
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 36 | 12 | 12 | 1.00 | Heidi Heitkamp (Democrat - ND) |
| 31 | 19 | 18 | 0.95 | Scott P. Brown (Republican - MA) |
| 56 | 17 | 16 | 0.94 | John Hoeven (Republican - ND) |
| 37 | 10 | 9 | 0.90 | Tim Kaine (Democrat - VA) |
| 242 | 34 | 30 | 0.88 | Lamar Alexander (Republican - TN) |
| 97 | 16 | 14 | 0.88 | Roger F. Wicker (Republican - MS) |
| 56 | 15 | 13 | 0.87 | Roy Blunt (Republican - MO) |
| 53 | 14 | 12 | 0.86 | Dean Heller (Republican - NV) |
| 186 | 56 | 48 | 0.86 | Wyche Fowler (Democrat - GA) |
| 188 | 20 | 17 | 0.85 | Johnny Isakson (Republican - GA) |
| 111 | 13 | 11 | 0.85 | John Barrasso (Republican - WY) |
| 54 | 6 | 5 | 0.83 | John Boozman (Republican - AR) |
| 48 | 12 | 10 | 0.83 | Mark Kirk (Republican - IL) |
| 695 | 125 | 104 | 0.83 | Daniel K. Inouye (Democrat - HI) |
| 381 | 34 | 28 | 0.82 | Pat Roberts (Republican - KS) |
| 192 | 87 | 71 | 0.82 | Lloyd Bentsen (Democrat - TX) |
| 168 | 37 | 30 | 0.81 | Albert Gore (Democrat - TN) |
| 287 | 37 | 30 | 0.81 | George Mitchell (Democrat - ME) |
| 241 | 63 | 51 | 0.81 | Lisa Murkowski (Republican - AK) |
| 37 | 5 | 4 | 0.80 | Brian Schatz (Democrat - HI) |
Top 20 Current Senators with the most votes against their own party: 1989-2015
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 6089 | 1631 | 1072 | 0.66 | Susan M. Collins (Republican - ME) |
| 8752 | 1249 | 514 | 0.41 | Richard C. Shelby (Republican,Democrat - AL) |
| 7992 | 1139 | 406 | 0.36 | John McCain (Republican - AZ) |
| 8915 | 833 | 346 | 0.42 | Chuck Grassley (Republican - IA) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
| 8784 | 822 | 491 | 0.60 | Harry Reid (Democrat - NV) |
| 3972 | 752 | 621 | 0.83 | Lisa Murkowski (Republican - AK) |
| 8676 | 709 | 404 | 0.57 | Orrin G. Hatch (Republican - UT) |
| 7558 | 607 | 391 | 0.64 | Dianne Feinstein (Democrat - CA) |
| 8777 | 592 | 196 | 0.33 | Patrick J. Leahy (Democrat - VT) |
| 6706 | 573 | 102 | 0.18 | James M. Inhofe (Republican - OK) |
| 8854 | 565 | 244 | 0.43 | Mitch McConnell (Republican - KY) |
| 5962 | 519 | 121 | 0.23 | Jeff Sessions (Republican - AL) |
| 8615 | 475 | 232 | 0.49 | Barbara A. Mikulski (Democrat - MD) |
| 4842 | 472 | 196 | 0.42 | Daniel Coats (Republican - IN) |
| 4765 | 470 | 324 | 0.69 | Thomas R. Carper (Democrat - DE) |
| 5950 | 454 | 107 | 0.24 | Michael B. Enzi (Republican - WY) |
| 7402 | 447 | 106 | 0.24 | Barbara Boxer (Democrat - CA) |
| 4033 | 432 | 337 | 0.78 | Lamar Alexander (Republican - TN) |
| 6299 | 430 | 204 | 0.47 | Ron Wyden (Democrat - OR) |
Top 20 Current Senators with the most successful votes against their own party: 1989-2015
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 6089 | 1631 | 1072 | 0.66 | Susan M. Collins (Republican - ME) |
| 3972 | 752 | 621 | 0.83 | Lisa Murkowski (Republican - AK) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
| 8752 | 1249 | 514 | 0.41 | Richard C. Shelby (Republican,Democrat - AL) |
| 8784 | 822 | 491 | 0.60 | Harry Reid (Democrat - NV) |
| 7992 | 1139 | 406 | 0.36 | John McCain (Republican - AZ) |
| 8676 | 709 | 404 | 0.57 | Orrin G. Hatch (Republican - UT) |
| 7558 | 607 | 391 | 0.64 | Dianne Feinstein (Democrat - CA) |
| 8915 | 833 | 346 | 0.42 | Chuck Grassley (Republican - IA) |
| 4033 | 432 | 337 | 0.78 | Lamar Alexander (Republican - TN) |
| 4765 | 470 | 324 | 0.69 | Thomas R. Carper (Democrat - DE) |
| 3909 | 416 | 244 | 0.59 | Lindsey Graham (Republican - SC) |
| 8854 | 565 | 244 | 0.43 | Mitch McConnell (Republican - KY) |
| 8615 | 475 | 232 | 0.49 | Barbara A. Mikulski (Democrat - MD) |
| 5919 | 421 | 226 | 0.54 | Pat Roberts (Republican - KS) |
| 2800 | 333 | 225 | 0.68 | Bob Corker (Republican - TN) |
| 7575 | 412 | 212 | 0.51 | Patty Murray (Democrat - WA) |
| 4703 | 362 | 212 | 0.59 | Bill Nelson (Democrat - FL) |
| 6299 | 430 | 204 | 0.47 | Ron Wyden (Democrat - OR) |
| 8777 | 592 | 196 | 0.33 | Patrick J. Leahy (Democrat - VT) |
Top 20 Current Senators with the highest success rates voting against their own party: 1989-2015
Note: only senators with more than 5 votes against their own party| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 354 | 23 | 20 | 0.87 | Mike Rounds (Republican - SD) |
| 1003 | 49 | 42 | 0.86 | Tim Kaine (Democrat - VA) |
| 1481 | 147 | 126 | 0.86 | John Hoeven (Republican - ND) |
| 3972 | 752 | 621 | 0.83 | Lisa Murkowski (Republican - AK) |
| 351 | 11 | 9 | 0.82 | Gary Peters (Democrat - MI) |
| 4033 | 432 | 337 | 0.78 | Lamar Alexander (Republican - TN) |
| 354 | 36 | 28 | 0.78 | Shelley Moore Capito (Republican - WV) |
| 355 | 19 | 14 | 0.74 | Thom Tillis (Republican - NC) |
| 977 | 150 | 109 | 0.73 | Jeff Flake (Republican - AZ) |
| 1483 | 230 | 167 | 0.73 | Kelly Ayotte (Republican - NH) |
| 8711 | 825 | 595 | 0.72 | Thad Cochran (Republican - MS) |
| 2356 | 217 | 155 | 0.71 | Roger F. Wicker (Republican - MS) |
| 1207 | 209 | 148 | 0.71 | Mark Kirk (Republican - IL) |
| 1473 | 154 | 108 | 0.70 | Rob Portman (Republican - OH) |
| 4765 | 470 | 324 | 0.69 | Thomas R. Carper (Democrat - DE) |
| 2800 | 333 | 225 | 0.68 | Bob Corker (Republican - TN) |
| 6089 | 1631 | 1072 | 0.66 | Susan M. Collins (Republican - ME) |
| 7558 | 607 | 391 | 0.64 | Dianne Feinstein (Democrat - CA) |
| 1434 | 168 | 108 | 0.64 | Roy Blunt (Republican - MO) |
| 3357 | 255 | 163 | 0.64 | Johnny Isakson (Republican - GA) |
Top 20 Current Senators with the highest success rates voting against their own party when it counted: 1989-2015
By "when it counted", I mean that these calculations are made in situations that required one or more Senators to vote against his or her own party for the result to have been what it was. For a detailed discussion of what this means, see the Code Book.Note: only senators with more than 5 votes against their own party
| All | Total | Successful | Success Pct | Senator |
|---|---|---|---|---|
| 36 | 12 | 12 | 1.00 | Heidi Heitkamp (Democrat - ND) |
| 56 | 17 | 16 | 0.94 | John Hoeven (Republican - ND) |
| 37 | 10 | 9 | 0.90 | Tim Kaine (Democrat - VA) |
| 242 | 34 | 30 | 0.88 | Lamar Alexander (Republican - TN) |
| 97 | 16 | 14 | 0.88 | Roger F. Wicker (Republican - MS) |
| 56 | 15 | 13 | 0.87 | Roy Blunt (Republican - MO) |
| 53 | 14 | 12 | 0.86 | Dean Heller (Republican - NV) |
| 188 | 20 | 17 | 0.85 | Johnny Isakson (Republican - GA) |
| 111 | 13 | 11 | 0.85 | John Barrasso (Republican - WY) |
| 54 | 6 | 5 | 0.83 | John Boozman (Republican - AR) |
| 48 | 12 | 10 | 0.83 | Mark Kirk (Republican - IL) |
| 381 | 34 | 28 | 0.82 | Pat Roberts (Republican - KS) |
| 241 | 63 | 51 | 0.81 | Lisa Murkowski (Republican - AK) |
| 37 | 5 | 4 | 0.80 | Brian Schatz (Democrat - HI) |
| 18 | 5 | 4 | 0.80 | Shelley Moore Capito (Republican - WV) |
| 767 | 122 | 94 | 0.77 | Thad Cochran (Republican - MS) |
| 757 | 85 | 65 | 0.76 | Barbara A. Mikulski (Democrat - MD) |
| 56 | 17 | 13 | 0.76 | Kelly Ayotte (Republican - NH) |
| 190 | 21 | 16 | 0.76 | Richard Burr (Republican - NC) |
| 51 | 12 | 9 | 0.75 | Marco Rubio (Republican - FL) |
Senators who are 2016 Presidential Candidates
Although all of Bernard Sanders votes were made as an Independent, I ran these calculations considering his vote as if he were a Democrat.
All Votes considered
| All | Total | Successful | Success Pct | |
|---|---|---|---|---|
| 2367 | 121 | 47 | 0.39 | Hillary Clinton (Democrat - NY) |
| 873 | 118 | 15 | 0.13 | Ted Cruz (Republican - TX) |
| 1287 | 161 | 61 | 0.38 | Marco Rubio (Republican - FL) |
| 2734 | 0 | 0 | 0.00 | Bernard Sanders (Democrat - VT) |
Only when it counted
| All | Total | Successful | Success Pct | |
|---|---|---|---|---|
| 197 | 7 | 4 | 0.57 | Hillary Clinton (Democrat - NY) |
| 32 | 7 | 2 | 0.29 | Ted Cruz (Republican - TX) |
| 50 | 12 | 9 | 0.75 | Marco Rubio (Republican - FL) |
| 131 | 0 | 0 | 0.00 | Bernard Sanders (Democrat - VT) |