While Republicans retain a plausible path toward taking control of the Senate on Tuesday night, it would involve their winning at least two seats in which they appear to be underdogs, while simultaneously avoiding upsets in several other races in which they are narrowly favored. Unless the Republicans have a significant wind at their backs and are overperforming in most parts of the country, their chances of doing so are slim.
The state that appears to have gotten away from Republicans is West Virginia, where Joe Manchin III, a Democrat running far to his right, appears to have created some space in the polls between himself and his Republican opponent, John Raese. Mr. Manchin has leads of 4 and 5 points in two new polls released within the past 24 hours, margins which — in recent years — have held up quite reliably on election day.
Mr. Raese’s chances are perhaps greater than the typical candidate in his position — in part because of the unusual dynamics of the election (Mr. Manchin has a 70 percent approval rating, but President Obama is overwhelmingly unpopular in the state) and in part because polling has been thin in the state, so the two surveys cannot quite be considered a consensus. Nevertheless, both polls showed Mr. Manchin’s position improving after he distanced himself from President Obama and virtually every major policy program on the Democratic agenda, and he now appears likely to win on the basis of his personal popularity: he has an 89 percent chance of doing so, according to the model.
Should Republicans be unable to win West Virginia, they would probably have to win both Washington and California to take over the Senate. In Washington, polling for their candidate, Dino Rossi, has improved somewhat in recent days, and one survey, from Public Policy Polling, gave him a 2-point lead.
Still, four other polling firms show Ms. Murray with a small lead instead, including one — Rasmussen Reports — which had previously given an advantage to Mr. Rossi. And polling has tended to underestimate the performance of Demcoratic candidates in Washington state in recent years. While the race is extremely tight and may not be resolved for several days as Washington counts mail ballots which were postmarked on election day, we show Ms. Murray as about a 2-point favorite which — at this late date — translates to a 79 percent chance of victory, although Mr. Rossi’s position has improved from several days ago.
California, meanwhile, looked to have gotten away from the Republican candidate, Carly Fiorina, in the last couple of weeks, and there is no clear sign of a reversal in the polling. While one company, Public Policy Polling, showed her deficit narrowing to 4 points from 9, another firm, SurveyUSA, had it growing instead to 8 points from 5. Ms. Fiorina is out of time, particularly given how many Californians have already voted by mail; the polling there is clear enough that a mistake, while possible, would be highly irregular.
Other hurdles that the Republicans would need to dodge include Nevada, Illinois, and Colorado, where their candidates appear to have small leads, although each one also provides some hope for Democrats. Their early voting numbers appeared to pick up late in the Nevada race, and private polling there reportedly has a more equivocal take on the race than the public polling does; a relatively high number of undecided voters remain in Illinois; in Colorado, where polling has been the closest of the three states, the effects of the governors’ race — where Tom Tancredo has become the de facto Republican nominee in lieu of Dan Maes — are hard to predict.
Democrats do not appear likely to pull off an upset in Wisconsin, where Russ Feingold seems bound to lose unless he can take great advantage of same-day registration in that state, or in Pennsylvania, where Pat Toomey seems to have held off a late charge by Joe Sestak and where Republican early voting was strong.
Alaska, however, could present a thorn in the side of Republicans. The polling there is extremely difficult to read, with many surveys having a partisan flavor and all of them having different techniques to handle Lisa Murkowski’s write-in candidacy. Our model, which penalizes Ms. Murkowski for being a write-in candidate, actually has her chances slipping slightly on the basis of a Public Policy Polling survey to show Joe Miller with a lead instead. The model also has Scott McAdams, a Democrat, who has by far the best favorability ratings of the three candidates, within striking distance with an 8 percent chance of victory.
Although it is difficult to say if this is a fair estimate of Mr. McAdams’s chances, he has pretty clearly become the Democrat with the best chance of picking up a Republican-held seat. It is plausible, in fact, that all other Democratic candidates who once seemed to have a chance of doing so, like Jack Conway of Kentucky and Paul Hodes of New Hampshire, will lose by double digits.
Because of the unusual dynamics of the race, it is also plausible that Mr. McAdams could win in Alaska even if Democrats were having a poor night over all, a situation that would have some analogy to 1994, when Tony Knowles became the only Democrat to pick up a Republican-held governorship in what was otherwise a terrible night for the party.
On the basis of these races, we have Republican chances of winning the Senate on Tuesday at just 7 percent, their lowest figure of the year.
However, Republicans have roughly even odds of finishing the night with at least 49 Senators, in which case they could conceivably lobby Ben Nelson, Democrat of Nebraska, and Joseph I. Lieberman, independent of Connecticut, to join their party at some point after the election.