Published: Apr 16, 2010 8:21 PM EDT

By BRENDAN FARRINGTON

AP Political Writer

Former Massachusetts Gov. Mitt Romney will endorse Marco Rubio over Gov. Charlie Crist in Florida's Republican Senate primary.

Romney plans to make the announcement on Saturday, according to a Romney adviser who wanted to remain anonymous because the announcement hasn't been made yet.

Romney is the third major 2008 presidential candidate to endorse Rubio. Former New York Mayor Rudy Giuliani and former Arkansas Gov. Mike Huckabee have also endorsed the former House speaker.

The adviser said Crist and Rubio both asked for the endorsement and Romney has spoken with each candidate, but Romney believes Rubio has a stronger conservative record and is an idea-driven leader.

Romney's PAC is contributing $5,000 to Rubio's campaign and the former governor plans to campaign with Rubio on Monday.

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