But six other states are holding primaries Tuesday, marking the virtual end of the long-running primary season. (Hawaii still remains; voters go to the polls there on Saturday.)
And in New Hampshire, another close race is being decided – also involving a "tea party" candidate taking on the establishment. But in this case, the dynamics are a bit more complex.
For one thing, backers are more split. Former state Attorney General Kelly Ayotte may be the GOP establishment's pick to take over Judd Gregg’s Senate seat, but she also has Sarah Palin’s endorsement. Ovide Lamontagne is the challenger to watch. He has the backing of most tea-party voters as well as the backing of Sen. Jim DeMint (R) of South Carolina, who, like Ms. Palin, has been busy backing national “antiestablishment” candidates this election season.
"Kelly is one tough ‘Granite grizzly’ who has broken barriers, fought off and locked up criminals, and stood up for New Hampshire families," Palin said in a robocall message to voters on Sunday. "She's the true conservative running for the US Senate in New Hampshire."
It’s always hard to gauge how much sway endorsements from national figures really have in a race. But it sets up an interesting test for Palin.
Ms. Ayotte is more moderate than Mr. Lamontagne, but this isn’t the first time Palin has gone against the typical tea-party choice. Also, she occasionally favors women who aren't as conservative as their opponents.
Ahead of the primary, most polls gave Ayotte a slim lead. If she takes the nomination, she’s likely to breeze to a victory in November over Rep. Paul Hodes, the uncontested Democratic candidate. Lamontagne, on the other hand, might face more of a battle.