Senate Forecast: What Has Gone Wrong for G.O.P. Candidates?
By NATE SILVER
The trend in the presidential race has been difficult to discern lately. President Obama has very probably gained ground since the conventions, but it’s hard to say exactly how much, and how quickly his bounce is eroding.
There are no such ambiguities in the race for control of the Senate, however. Polls show key races shifting decisively toward the Democrats, with the Republican position deteriorating almost by the day.
Since we published our initial Senate forecast on Tuesday, Republicans have seen an additional decline in their standing in two major races.
Two polls of
Virginia published on Wednesday gave the Democrat, the former Gov. Tim Kaine, leads of 4 and 7 percentage points over the Republican, the former Senator George Allen. The FiveThirtyEight forecast model now gives
Mr. Kaine roughly a 75 percent chance of winning the seat on the strength of the new polls, up from about 60 percent in Tuesday’s forecast.
The other problematic state for Republicans is
Wisconsin, where their candidate, the former Gov. Tommy Thompson, had once appeared to hold the advantage.
Mr. Thompson’s Democratic opponent, Representative Tammy Baldwin, had published an internal poll earlier this week showing her pulling into the lead. The FiveThirtyEight Senate and presidential forecasts do not use internal polls released directly by the campaigns, as they typically exaggerate their candidate’s standing.
However, in this case, public polls have now confirmed that the race seems to have shifted. A poll by The New York Times, CBS News and Quinnipiac University showed Mrs. Baldwin having drawn into a tie with Mr. Thompson, after trailing him by 6 percentage points last month.
A Marquette University poll, also published on Wednesday, showed a much sharper reversal, with Mrs. Baldwin going from a 9-point deficit to a 9-point lead. The Marquette poll appears to be a bit of an outlier — it also had Mr. Obama leading in the presidential race in [b]Wisconsin[/b[ by a 14-point margin, a somewhat implausible figure. Nonetheless, the model now has
Mrs. Baldwin as the slight favorite, with about a 60 percent chance of winning.
It would be only a modest exaggeration to say that it’s been hard to find any strong Senate polls for Republicans in the past two or three weeks.
Wednesday also brought bad news for Republicans in Massachusetts, where a fourth consecutive poll showed the Democrat Elizabeth Warren ahead of Senator Scott Brown; in Connecticut, where a poll gave the Democrat Chris Murphy a slight advantage over their candidate, Linda McMahon; and in Florida, where a Fox News poll gave the Democratic incumbent Bill Nelson a 14-point lead.
One exception has been
in Maine, where two new polls on Wednesday showed a deterioration in the standing of the independent
Angus King, who would probably caucus with the Democrats, at the expense of both the Republican, Secretary of State Charles Summers, and the Democrat, State Senator Cynthia Dill. The model now gives Mr. King an 84 percent chance of winning, Mr. Summers 11 percent, and Mrs. Dill 5 percent.
But this is small compensation for the decline over the past two weeks of the Republicans’ position in Virginia, Massachusetts, Wisconsin, Florida and Ohio, all of which have broken sharply to the Democrats.
The Democrats’ chances of controlling the Senate have increased to 79 percent in the forecast, up from 70 percent on Tuesday.
Had we run the model a month ago, based on polls through Aug. 19, the Democrats’ chances of maintaining Senate control would have been listed at just 39 percent....