Eleven Republican seats up next year are considered safe; three need watching. Maine’s Susan Collins is the only GOP incumbent running in an Obama state, but she’s personally popular and an effective campaigner. Mitch McConnell understands that while Kentucky is a Republican presidential stronghold, every state capital office but one is occupied by a Democrat. That’s why he’s raised more money than any other senator up in 2014. Avoiding serious primaries is important if the GOP is to retain Maine and Kentucky. Georgia will have a big primary but should remain Republican unless a candidate ill-suited for the general election sneaks through the primary.

Open seats are more likely to flip, and so far only two Republicans are retiring (Georgia’s Saxby Chambliss and Nebraska’s Mike Johanns) while six Democrats are, including three in states handily carried by Mr. Romney (West Virginia, South Dakota and Montana). Republican Rep. Shelley Moore Capito, a terrific campaigner, is running in West Virginia while former Gov. Mike Rounds is running in South Dakota. If Mr. Rounds faces a first-tier Democratic opponent, he’ll have to raise more money and mount a stronger campaign than in his gubernatorial races.

Republicans will be competitive in Democratic open seats in Iowa, Michigan and Montana if they recruit top-quality candidates like Rep. Mike Rogers, who’s considering a run for Michigan’s open seat.