Why Florida's Senate race is going to be so much fun to watch.

The problem for the GOP is that its right wing quickly decided that the good news was very bad news indeed.

But conservatives, who have long mistrusted Crist, now loathe him for committing the cardinal sin of enthusiastically endorsing President Obama's stimulus plan earlier this year. Among right-wing stalwarts, even using the word "stimulus" is a wicked act. They insist on the ugly locution "porkulus," as in political pork.

Marco Rubio, the former Florida House speaker, will be the conservatives' champion in the primary. In this age of instant communications, Rubio answered Crist's announcement with an online ad in what might be called an abstract expressionist style.

Keep an eye on Rubio, a bright, handsome 37-year-old son of Cuban immigrants. He was mentored by none other than former Gov. Jeb Bush. As soon as Crist announced, Florida political junkies went into overdrive speculating whether Bush would endorse Rubio and turn the primary into a brawl. Rubio is already being touted as the orthodox right's answer to Obama, and even his adversaries respect his talents.

National Republican leaders certainly hope so because they went out on a limb for Crist almost as soon as he had finished his brief announcement (which, by the way, echoed Bill Clinton in touting the need to "put people first").

Conservative blogs were quick to take Cornyn to task. "Instead of trying to beat conservatives," John J. Miller harrumphed on National Review's "The Corner" blog, "the NRSC should save its resources for defeating Democrats." Oh, this one will be fun.

David Winston, a Republican pollster, said Cornyn has learned from Sen. Charles Schumer, who led the Democrats' successful campaign to take back the Senate in 2006. Schumer was willing to battle local Democrats--his support for Bob Casey, a pro-life Democrat in Pennsylvania, was emblematic--to force the nomination of the most electable candidate.

Still, Florida will be one of the clearest tests of whether rank-and-file Republican voters are more interested in doctrinal purity, or in winning--even if it means nominating an Obama hugger.

E.J. Dionne, Jr. is the author of the recently published Souled Out: Reclaiming Faith and Politics After the Religious Right. He is a Washington Post columnist, a senior fellow at the Brookings Institution, and a professor at Georgetown University.

By E.J. Dionne, Jr.