Dino Rossi is still weighing his options when it comes to challenging Sen. Patty Murray (D-Wash.), but it might be too late, according to recent history.

A Smart Politics analysis shows that no candidate in the last decade has launched his or her campaign after April 3 of the election year and gone on to victory. And the man who entered the race the latest -- former Minnesota Sen. Mark Dayton (D) -- had gobs of money to throw at it.

Besides Dayton, the latest entry for a winning Senate candidate came from now-Interior Secretary Ken Salazar, who got in the 2004 Colorado Senate race on March 10 of that year.

Rossi, meanwhile, has entertained the idea of waiting until the June filing deadline to launch a campaign against Murray. He said he can quickly tap all his old donors and have a solid electoral base to start with, by virtue of his two unsuccessful gubernatorial campaigns in 2004 and 2008.

That all may be true, but Republicans appear to be getting nervous about Rossi waiting too long. National Republican Senatorial Committee (NRSC) Chairman John Cornyn (R-Texas) told The Hill recently that he'd like Rossi to make a decision sooner than later, so that both the candidate and the committee can get their house in order.

“I’ve been urging him to make a decision sooner rather than later because there’s a practical problem with not having enough time to do what you need to do before the election," Cornyn said.

As a side note, the longest campaign for a winning Senate candidate was Sen. Bob Corker's (R-Tenn.) 2006 campaign. He announced more than two years early, in October 2004.