Could Sen. McConnell lose? He'd be in good company, historically.

If Senate minority leader Mitch McConnell loses his seat this fall, his downfall is bound to be compared with those of other powerful figures in Congress. But the only commonality is likely to be that they all lost.

Here’s why Mr. McConnell’s case differs from that of:

Tom Daschle. The former Democratic senator from South Dakota served as both majority and minority leader. He lost reelection in 2004 in a close race with Republican John Thune, who tarred him as an “obstructionist.” McCon-nell bears the same label. But Mr. Daschle blocked President George W. Bush while representing a state that ended up voting for him – twice. McConnell is fighting the unpopular President Obama, who lost Kentucky by wide margins in 2008 and 2012.

Daschle ignored his state’s conservative leanings; McConnell is in sync with them.

Richard Lugar. Until his defeat in 2012, Mr. Lugar was the most senior Republican in the Senate. He lost his primary race to an upstart tea party candidate, Indiana Treasury Secretary Richard Mourdock, who later lost in the general election.

When Mr. Mourdock announced his candidacy, he presented a list of 67 GOP county chairs who endorsed him. In the Kentucky state legislature, 64 of 68 Republicans have endorsed McConnell over tea party underdog Matt Bevin. Why? Because McConnell basically built the GOP in Kentucky, and is involved at the local level with new generations of Republicans.

Lugar didn’t water his GOP garden; McConnell keeps the sprinklers on.

Tom Foley. The former Democratic speaker of the House from Washington State lost his seat in 1994. One reason was that his Republican opponent, George Nethercutt, raised a storm over Mr. Foley’s decision to run for a 16th term, even though Washington voters clearly favored term limits.

Another reason: Foley was swimming against a tide of red, the Republican Revolution of 1994. McConnell, unlike Foley, is swimming with the tide. Republicans are favored to pick up Senate seats, if not win control of the Senate this fall.

McConnell may still lose. He is in a dead heat with his Democratic opponent, Alison Lundergan Grimes. But if he does, it won’t be for the same reasons these other powerful leaders lost.