Rep. Joe Sestak's announcement that, assuming his family agrees, he will challenge Arlen Specter makes next year's primary season one to watch. Word got out after TPM got their hands on a hand-written donor letter, but Sestak made the cable-TV run last night confirming the decision. Sestak has been polling well behind Specter, but you have to guess he has internal numbers suggesting he can make up that ground by improving his name ID and pushing some of Specter's previous votes.

The meme on Sen. Chris Dodd seems to be that it's "still ugly," but he's made up huge amounts of ground on Republican challenger Rob Simmons, who hasn't done much in the fundraising department. The question stands whether Dodd, too, will get primaried, as Hartford businessman Merrick Alpert is polling at 24 percent against Dodd despite being almost totally unknown. Dodd, though, still has powerful supporters that Alpert will have to overcome.

The interesting primary on the Republican side will be Florida, where popular Gov. Charlie Crist, who is supposed to be the party's moderate savior, is facing a challenge from the right by former state House Speaker Marco Rubio. Despite NRSC support for Crist, Rubio is garnering big-name endorsements, first from Huckabee and now from Jeb Bush, Jr. And with Sonia Sotomayor's nomination (which is polling well) highlighting the party's Latino problem, Rubio, a Cuban-American, could stand to gain.

Sotomayor's dominating news presence may fade fast, though, as no senator has yet lined up squarely against her. She may, in fact, face as many criticisms from the left as some abortion-rights activists worry about her vague positions.