He was elected in 2004, so he didn't even serve one term. Kind of like another Republican I can think of, from the opposite corner of the country. Simon Rosenberg has a nice capsule review of Martinez's career in the Senate (via Kos). George W. Bush appointed him as chair of the RNC to try to woo the Hispanic vote. He lasted less than a year in that job. Somehow not surprising.
John Ridley in HuffPost thinks Martinez's timing was meant to send a strong signal:
It's very, very hard not to see the timing as a statement. Not just against the Republican's attempted debasement of Sotomayor, and by association the Hispanic narrative in America. Martínez's move, too, can been seen as another accomplished person of color -- following Colin Powell -- flipping a metaphorical middle finger at all the Republicans have devolved into.Family and culture are apparently stronger than ideology for Martinez. As they are for most people. Business ties are also presumably stronger. I know next to nothing about the man, but if he's from Florida, I can guess that that's where most of his contacts are. Many of those contacts are, presumably, Hispanic, and my guess is that he has been hearing some strong opinions from fellow Hispanics in Florida. He was probably facing ever-more pressure to make a choice between his party and his friends and family. By resigning the day after his vote for Sotomayor, he makes it as clear as possible that he was waiting for that vote to resign. Which, of course, means that he wanted to make a strong statement about where his allegiance lies. It ain't with the GOP.