While Republicans’ position is holding steady in the House — where they are 4:1 favorites to win control of the chamber according to our analysis — their chances of also taking over the Senate declined in today’s forecast. Those chances are now 16 percent, down from 19 percent in our forecast over the weekend.
The modest decline in the Republicans’ chances today is a result of new polling in two states. The first is Colorado, where two new polls, from Public Policy Polling and SurveyUSA, each show the exact same result, with the Republican, Ken Buck, and the Democrat, Michael Bennet, tied at 47 percent each. Colorado had appeared to slightly favor Mr. Buck for most of the cycle, with his winning chances peaking at 79 percent in our Sept. 30 update. Since then, however, he has endured some decline after a series of minor gaffes, with polls suggesting that Mr. Bennet may have improved his standing among female voters. We now project Colorado’s Senate race to be the closest in the country — slightly closer than others like Nevada or West Virginia. Mr. Buck is now an 0.4-point favorite, according to the model, and his chances of winning are 54 percent.
The other significant move today is in West Virginia, and it is toward the Democrat, Joe Manchin, as a Public Policy Polling survey gives him a 6-point lead over Republican John Raese.
The West Virginia forecast has been fairly volatile, as polls there have been relatively rare and as they’ve often been at odds with one another. In particular, 6 out of 10 polls from the firm Rasmussen Reports have shown Mr. Raese with a lead, while 6 out of 7 polls from firms other than Rasmussen have shown Mr. Manchin tied or ahead.
In this case, I’m inclined to put some credence in Public Policy Polling’s numbers, because they find the gain in Mr. Manchin’s support to have come from conservative voters, after he has tacked very hard to the right — for instance, in declining to endorse President Obama for a second term. One almost get the sense that Mr. Manchin is bound to win his race, but then be a thorn in the side of Democrats for at least the first two years of his tenure in the Senate, after which time he’d face re-election again. Mr. Manchin is now a 66 percent favorite, up from 50 percent last week.
Two other important states show slight movement tonight toward the candidate who had already appeared to hold the lead.
In Illinois, a Chicago Tribune poll gives the Republican, Mark Kirk, a 3-point lead over Alexi Giannoulias. This is the fourth consecutive survey to show Mr. Kirk with a lead, and he can now be thought of as a slight favorite. Because of the unusually high number of undecided voters in the state, however, Mr. Giannoulias retains a potential path to victory by turning out the Democratic base.
Finally, in California, a poll for the University of Southern California and the Los Angeles Times gives the Democrat, Barbara Boxer, an 8-point lead over Carly Fiorina. This does not have a tremendous impact on the model, because the poll has consistently shown good numbers for Ms. Boxer and her fellow Democrat, Jerry Brown. But her probability of winning is now up incrementally to 84 percent from 82 percent.
Republicans could clearly still win the Senate, although since Connecticut now appears completely off the table, the path will have to involve two of three states — West Virginia, California, and Washington — where Democrats are now favored, while holding Colorado, Illinois, and Nevada. This is not an easy task and it increasingly appears that Republicans might need to have a wind at their backs to accomplish it — that is, to be overperforming their polling across the board nationally (a possibility that our model very explicitly accounts for).