A new report shows defeating Republican Sen. Mitch McConnell of Kentucky in this year’s election would be a historical rarity given his status as minority leader.
An analysis of Senate elections over the past 90 years by the Humphrey School of Public Affairs at the University of Minnesota finds sitting party leaders have won re-election 87 percent of the time.
In only one case has a minority leader—Democrat Tom Dashcle in 2004—lost a re-election bid.
First elected in 1984, McConnell has been GOP leader for the past seven years.
In the fall election he faces a primary opponent in Matt Bevin and a formidable general election challenge from Democrat Alison Lundergan Grimes.
University of Minnesota political science professor Eric Ostermeier, who compiled the study, says those negatives could prove fatal, but that history and projections of Republicans gains in the Senate benefit McConnell.
"A McConnell loss in a cycle in which the Republican Party, most prognosticators would suggest are going to pick up some seats, this would be unprecedented. In the four instances in which a floor leader has lost in all of those cases his party has also shed seats that cycle," he says.
The study puts in perspective just how difficult it is to defeat a party leader, but also how McConnell's position is becoming less of a guarantee for incumbency.
For instance, no floor leader has ever been defeated in a primary election or received less than 75 percent of the vote. But Ostermeier says polls indicate Bevin is likely to break that threshold in the May primary.
Overall, just four Senate leaders have lost re-election in the country's history since the direct vote era began. But the report shows they are more vulnerable than ever as the public's disgust with Congress grows.
The last three re-elections involving Senate majority or minority leaders have been some of the more competitive contests in the past four decades.
Both McConnell and Senate Majority Leader Harry Reid won their previous races by just six points, and Daschle lost by just under two points in 2004. In previous decades, party leaders were winning by 25 to 40 point margins consistently.
A chief argument made by McConnell personally is that it would be wrongheaded for Kentucky voters to replace a veteran party leader with influence for a "rookie" in Grimes.
"It could be a reflection of these positions being the face of the parties in an ever increasingly partisan and unpopular institution. And (party leaders) facing higher and higher negative approval ratings not only nationally, but trickling down and also in their home states," says Ostermeier.
"History is on McConnell's side, but we have seen aberrations to historical trends in recent cycles. McConnell can't take necessarily comfort in the fact that history is on his side. But it's certainly an interesting trend and suggestive of the difficulty in knocking off these leaders."