In Massachusetts Senate Race, Odds for G.O.P. Upset Are Slim – NYTimes.com

How likely is a candidate to overcome a polling deficit in the range of nine percentage points with so little time remaining in the campaign? I searched through our Senate polling database, which covers all November elections for Senate between 1990 and 2012, looking for those candidates who overcame the largest deficit in the polls with 10 days to go in the race. (I limited the search to cases where it was actually possible to construct a polling average rather than relying upon a single poll — meaning those where there had been at least two polls in the field late in the race.)

The award for the largest comeback belongs to Paul Coverdell, the Republican candidate in the Georgia election for Senate in 1992. Mr. Coverdell overcame a huge polling deficit to defeat the Democratic incumbent, Wyche Fowler Jr., having trailed him by 24 percentage points with a month remaining in the campaign and by roughly 19 percentage points in the polling average with 10 days to go. However, Mr. Coverdell’s win requires an asterisk of sorts, as Mr. Fowler took the narrow plurality of the vote on Nov. 3, 1992, triggering a runoff that Mr. Coverdell won three weeks later.

In Georgia’s Senate race in 2002, the Republican candidate, Saxby Chambliss, trailed the Democratic incumbent, Max Cleland, by eight percentage points in the polling average with 10 days remaining in the race. But Mr. Chambliss wound up winning by a clear margin, roughly seven percentage points. (It’s possible that this reflected a case of social desirability bias as some voters were reluctant to tell pollsters about their plans to vote against Mr. Cleland, a triple amputee and war hero.)

So such last-minute comebacks are not impossible. But they are unlikely — these results are plucked from a database that covers approximately 400 Senate races. From an actuarial perspective — based on an analysis of the accuracy of the polling average in each of the several hundred races — the probability of winning a race after trailing by nine points with 10 days to go in the campaign is on the order of 5 percent.

via In Massachusetts Senate Race, Odds for G.O.P. Upset Are Slim – NYTimes.com.