WASHINGTON (AP) — He's been running for president for quite a while -- but Mitt Romney says, "The campaign started yesterday -- the general election campaign."

His comments to Fox News came a day after his chief Republican rival, Rick Santorum, announced he was ending his own campaign for the nomination.

Romney had been asked how he would counter continued Democratic attacks that he is an out-of-touch rich guy. He responded that it's "a little early in the process."

The former Massachusetts governor said conservatives will unite behind him -- and that he believes Santorum will campaign with him against Obama.

He also suggested that he is considering one of his former rivals to be his running mate. Romney says the party has a lot of "extraordinary leaders," including some who have run for president.