Mel Martinez resigns:

"Twelve years ago I offered myself as a candidate for public office in Florida out of a deep sense of appreciation for what America and the people of Florida did for me as a young immigrant to this country.

In 1997, Kitty and I decided it was time to give back and we entered the public arena, first as mayor of Orange County, then as a member of the President's cabinet and now as a United States Senator. Through those experiences I have gained the greatest respect for the people of Florida and have enjoyed having served their interests.

When I began my term as Senator, I promised I wouldn't simply warm a seat; I promised to take on the difficult issues and work to make a difference. Keeping that promise has meant a pressing for help and assistance for families struggling to keep their homes, their jobs, and their confidence that our country is safe.

And on that note, I am especially grateful to the men and women of our military and their families whom I've had the distinct honor of representing in Washington and I thank them for their service to our country.

As a US Senator, I have also had a platform to speak against the oppression of the Cuban regime and my hope for a better future for the people of Cuba. I will continue that lifelong passion in the next phase of my life.

I will always be grateful to the people of Florida for bestowing on me the singular honor of representing them in the United States Senate.

My priorites have always been my faith, my family and my country and at this stage in my life, and after nearly 12 years of public service in Florida and Washington, it's time I return to Florida and my family.

So today I'm announcing my decision to step down from public office, effective on a successor taking office to fill out the remainder of my term.

I have enjoyed my time in the Senate and have the utmost respect for my colleagues and the institution. I especially thank Republican leader Mitch McConnell for his guidance and insight.

I look forward to continueing to be an active and constructive voice on issues vital to Florida and our nation, and being an active member of Florida's Republican Party."

Update: Excellent commentary, as always, from Ed Morrisey:

What will Crist do? He certainly won’t appoint himself. He has the authority to do it, but it would not sit well with his constituents to make such a self-serving play. Crist won’t appoint Marco Rubio, either, because he has no intention of running against Rubio in a primary after making him an incumbent. He will need a safe, popular choice, one that poses no political risk for Crist while ensuring that the seat will be open in a Republican primary.

I’d guess that Crist will ask Jeb Bush to take the job. Bush has not indicated any interest in the Senate seat, which is one of the reasons why Crist felt comfortable in running for it. Despite the negatives associated with his brother, Jeb’s popularity remains high in Florida, and his replacement of Martinez will make Florida’s representation a little more conservative for the next year. Bush won’t mind mixing it up with the Obama administration, either. Crist could get Bush’s popularity to rub off on himself for his own Senate run next year.

Statement from Marco Rubio:

MARCO RUBIO COMMENTS ON SEN. MEL MARTINEZ'S RESIGNATION

Miami, FL – U.S. Senate candidate and former Florida House Speaker Marco Rubio today issued the following statement regarding U.S. Sen. Mel Martinez's resignation:
"Mel Martinez's life is a testament to the boundless promise that exists in America, where a young Cuban exile can come to the United States without his parents and rise to become a Cabinet secretary and U.S. senator. As he looks ahead towards the next phase of his life, I wish him and his family all the best.

"As Governor Crist considers who he will appoint as Florida's next U.S. senator, I urge him to take great care in his selection. Florida deserves an interim senator who will go to Washington and serve as a true check on President Obama's push for more wasteful government spending, government-run health care and cap-and-trade. The last thing Florida needs is a U.S. senator that will stand with President Obama instead of challenging the wrong direction he is leading our country and offering constructive conservative solutions moving forward."

H/T Daniel P.