“He said it just wasn’t the right timing,” [Marco] Rubio said, recounting a phone call he received this afternoon from the former Florida governor and presidential brother.

Bush, who left office in 2007, cited his desire to explore other professional opportunities outside of politics, Rubio said.

Rubio, a close Bush ally who was waiting on the former governor’s decision, said he would now “seriously explore the opportunity.”

The timing’s never going be right for Bush, apparently: He passed up a challenge to first-term Senator Ben Nelson (D) in 2006, too. (This inaugurated one of my favorite no-hope political drafts of the cycle: Quin Hillyer’s lonely quest to bring Jack Nicklaus into politics.)

But 2010 looked like a much better year. Gov. Charlie Crist (R) will be on the ballot, probably against a token Democrat. With the exception of the 9/11-boosted George W. Bush in 2002, the Cuban Missile Crisis-aided JFK in 1962, and the New Deal-boosting FDR in 1934, first presidential midterms always mean a voter backlash against the incumbent party: 2010 promises to be the best Republican year in Florida since 2004.

It’s easy to draw the conclusion, as a lot of conservatives have, that Bush is a thoroughbred executive who would be bored by the Senate. Or, as W. James Antle III suggests: “Maybe his dad embarrassed him.”