34 Senatorial seats were up for election in November. I computed the expected probabilities of winning for each incumbent, based on the "Model 2" estimates in Gowrisankaran, Mitchell, and Moro (2004), Table 3. These probabilities are solely based on the history of the seat; other circumstances such as party membership, and other indicators of candidates' quality are not used in these computations.
Not all incumbents were running. For those that were not running, the table reports their predicted probability of re-election if they had chosen to run. For example, if vice-presidential candidate John Edwards (D,NC) had chosen to run, his re-election probability would be the lowest among the current incumbents, with 67%. Five-term incumbent and open seat winner Patrick Leahy (D,VT) has the highest probability of winning, with 90.3%.
Democrats are incumbents in 18 out of 34 seats. 5 democrats and 3
republicans are not seeking re-elections. According to our
predictions, if all incumbents had run, democrats would be expected to
win 18.57 races. Assuming that each candidate in open-seat elections
wins with probability 0.5, democrats are expected to win 17.97 races.
The current U.S senate has 51 republicans, 48 democrats, and 1
independent that votes with democrats.
According to these probabilities (and assuming that open seats are
assigned with probability 50/50), republicans had 75% probability of
retaining control of at least 51 seats.
Only one incumbent, Tom Daschle (SD) lost the election
| State | Incumbent | Party | Chain* | Probability | Win? |
|---|---|---|---|---|---|
| CT | DODD, CHRISTOPHER J. | D |
4 | 0.784 | YES |
| NH | GREGG, JUDD | R |
2 | 0.822 | YES |
| VT | LEAHY, PATRICK | D |
5 | 0.903 | YES |
| NY | Schumer, Charles | D |
4 3 1 | 0.769 | YES |
| PA | SPECTER, ARLEN | R |
4 | 0.784 | YES |
| IL | Fitzgerald, Peter** | R |
2 1 1 | 0.720 | - |
| IN | Bayh, Evan | D |
1 | 0.768 | YES |
| OH | Voinovich, George | R |
1 | 0.768 | YES |
| WI | FEINGOLD, RUSSELL D. | D |
2 1 1 4 3 2 2 | 0.797 | YES |
| IA | GRASSLEY, CHARLES E. | R |
1 4 | 0.718 | YES |
| KS | BROWNBACK, SAM | R |
2 | 0.822 | YES |
| MO | BOND, CHRISTOPHER | R |
3 | 0.837 | YES |
| ND | DORGAN, BYRON | D |
2 | 0.822 | YES |
| SD | DASCHLE, THOMAS ANDREW | D |
3 1 3 | 0.798 | NO |
| AL | SHELBY, RICHARD CRAIG | R |
1 3 | 0.786 | Yes |
| AR | Lincoln, Blanche | D |
1 | 0.768 | YES |
| FL | GRAHAM, BOB** | D |
1 1 3 | 0.769 | - |
| GA | Miller, Zell** | D |
1 | 0.768 | - |
| LA | BREAUX, JOHN B.** | D |
3 | 0.837 | - |
| NC | Edwards, John** | D |
1 1 1 | 0.670 | - |
| SC | HOLLINGS, ERNEST** | D |
1 6 | 0.882 | - |
| KY | Bunning, JAmes paul david |
R |
1 | 0.768 | YES |
| MD | MIKULSKI, BARBARA | D |
3 | 0.837 | YES |
| OK | NICKLES, DON** | R |
4 | 0.784 | - |
| AZ | MCCAIN, JOHN S | R |
3 | 0.837 | YES |
| CO | CAMPBELL, BEN NIGHTHORSE** | R |
2 | 0.822 | - |
| ID | Crapo, MiChael D. |
R |
1 | 0.768 | YES |
| NV | REID, HARRY M. | D |
3 | 0.837 | YES |
| UT | BENNETT, ROBERT F. | R |
2 | 0.822 | YES |
| CA | BOXER, BARBARA | D |
2 | 0.822 | YES |
| OR | WYDEN, RONald lee |
D |
2 | 0.822 | YES |
| WA | MURRAY, PATTY | D |
2 | 0.822 | YES |
| AK | (Murkowski, Lisa)*** | R |
- (2 2 4) | (0.5) | - |
| HI | INOUYE, DANIEL KEN | D |
1 7 | 0.892 | YES |
*CHAIN: The column labeled "chain" reports the history of the senatorial seat since the last open seat election; each digit represent the number of elections a senator in the chain won: for example, NY senator Chuck Shumer's chain is 4-3-1. This means he is the third senator since the last open seat election. He is a 1-term incumbent, who beat a 3 term incumbent, who beat a 4 term incumbent.
