Let’s narrow it down further, to only races in which the incumbent ran for re-election. Except for Georgia’s Saxby Chambliss and Nebraska’s Mike Johanns, all Republican incumbents are running for re-election, at least at this point. The incumbents include, of course, Mitch McConnell, who has to defend his seat in Kentucky.
Of these senators, only one incumbent out of 63 has gone down since 1982: Lauch Faircloth, in 1998. For those who don’t remember, Faircloth was a protege of the very conservative Jesse Helms. He lost to John Edwards, who was then a trial lawyer.
Without controlling for incumbency, the odds get even worse for the president’s party when he can’t break a 60% approval rating. Since 1982, there have been 57 elections in which the opposition held a seat in a state more partial to their party’s presidential candidate than the national vote. The opposition party lost none of those 57 elections.
None of these numbers should comfort Democrat challengers in 2014. The chances for any Democrat to win a red state (or for a Republican to win in a blue one) have decreased dramatically over the past 20 years. If you’re challenging a candidate from the opposition party in a midterm, your chances drop to around 4%. If you’re also facing an incumbent, your odds inch even closer to nil.