Florida Governor Charlie Crist announced his candidacy for Mel Martinez’s Senate seat today, which should have been the big political news of the day.  Instead, the NRSC overshadowed Crist by endorsing him as a primary candidate, even though state House Speaker Marco Rubio had already announced his bid for the job.  Conservatives may well wonder why the NRSC has interfered in a GOP primary:

Gov. Charlie Crist announced his candidacy for U.S. Senate this morning, becoming the first Florida governor in decades to decline a re-election bid for a shot at moving to Washington, D.C.

Crist, 52, told reporters in a Capitol news conference that the “challenges that Florida faces are not just Florida challenges. They’re national challenges.” “And as a result of that, I believe I can best serve the people of Florida, if they’re willing to allow me, as their next United States senator,” said Crist, a Republican.

The U.S. Senate seat is being vacated by retiring Sen. Mel Martinez, R-Fla., creating a coveted opening. While Crist would only be eligible for one more term as governor because of term limits, U.S. senators often stay for life.

Tradition dictates that the national organizations remain neutral in primary races.  The NRSC relied on precisely that tradition in 2004 when they refused to get involved in Pat Toomey’s challenge to Arlen Specter, and in 2006’s Rhode Island primary that pitted Lincoln Chafee against conservative Steven Laffey.  In that race, the NRSC actually ran ads for Chafee during the primary, explaining that they support incumbents.

But the incumbent in this race is retiring, which makes this statement from John Cornyn all the more inexplicable:

“I am pleased today to endorse Gov. Charlie Crist for the United States Senate. With his record of reform in Florida, I know that Gov. Crist will bring a fresh perspective to Washington in our efforts to fight for lower taxes, less government and new job creation for all Americans. Charlie Crist is a tireless advocate on behalf of all Floridians and one of only three Governors who earned an ‘A’ from the CATO Institute for his efforts to restrain spending and cut taxes last year,” Cornyn said.

“While I believe Marco Rubio has a very bright future within the Republican Party, Charlie Crist is the best candidate in 2010 to ensure that we maintain the checks and balances that Floridians deserve in the United States Senate. Gov. Crist is a dedicated public servant and a dynamic leader, and the National Republican Senatorial Committee will provide our full support to ensure that he is elected the next United States Senator from Florida.”

It smacks of a deal cut to get Crist to skip a re-election campaign to go after the Senate seat.  While Crist’s popularity is an asset, Crist’s positions on issues are going to give conservatives and even moderates some angst in the party.  Crist openly supported the Porkulus plan, which would have put him with Arlen Specter, Olympia Snowe, and Susan Collins as the only Republicans in Congress who did.  Cornyn himself fought against Porkulus.  So why is the NRSC endorsing Crist over Marco Rubio 15 months ahead of the primary?

Update: Nate Silver wonders whether Democrats ought to bother with a serious challenge if Crist wins the primary.  Read it all, but here are a couple of points for the GOP to ponder:

The Stimulus. Crist was in favor was in favor of Obama’s economic stimulus package, and in fact campaiged with the President for its passage.

Cap-and-Trade. Crist supports cap-and-trade and signed a bill to create a statewide cap-and-trade system in Florida. This isn’t necessarily that radical a stance for a Florida politician, a state which has relatively few jobs in carbon-intensive industries and conversely might suffer disproportionately from rising sea levels and stronger Atlantic hurricanes (Mel Martinez, Florida’s outgoing Senator, was one of seven Republicans to vote in favor of cloture on last year’s climate change bill). Crist also somewhat notoriously reversed his former opposition to offshore drilling during John McCain’s 2008 election campaign. Nevertheless, he is likely to be a reasonably reliable Democratic vote on environmental issues.

National Health Insurance. Unclear. Last May, Crist signed a bill to provide for low-cost, no-frills health insurance for the roughly 20 percent of Floridians who are uninsured. The bill does not contain an individual mandate, but does prohibit insurance companies from discriminating on the basis of age or pre-existing conditions. The smart money is that Crist would be a gettable vote on health care but would balk at a public option.