Romney moves to consolidate GOP support, court ex-rivals' backers

Now, the hard part.

Mitt Romney, after finally clearing away the competition in the long and winding Republican primary battle, is turning to consolidate the support of the GOP base, which he'll need to challenge President Obama in what is expected to be a bitter and divisive White House campaign.

The campaign already is reaching out to secure the support of the myriad networks backing his former rivals. If all goes well for the Romney camp, endorsements from the candidates themselves will follow.

One source told Fox News on Wednesday that Gingrich will "more than likely" endorse Romney when he announces next week that he is leaving the race.

Timing on a possible endorsement from Rick Santorum, who bowed out earlier this month, is less clear, though Fox News confirms that Santorum and Romney plan to meet on May 4.

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Courting the conservative base, though, is more complicated that just securing those endorsements. That's why the campaign has brought on dedicated staffers whose job it is to reach out to constituency groups -- like evangelicals, who until recently were largely backing Santorum. This operation has been under way for weeks.

The campaign also is courting some of the other candidates' biggest fundraisers. Sheldon Adelson, the wealthy casino magnate who almost single-handedly stood up Gingrich's super PAC, has indicated he will back Romney, as has Santorum's super PAC sponsor Foster Friess.

Asked for comment, a Romney campaign official expressed confidence that the party was "uniting behind" the former Massachusetts governor.

"Voters are uniting behind real change -- and that change is Governor Romney," the official told

Romney pivoted clearly to the general election Tuesday night in a New Hampshire speech following his five-state primary sweep.

"To all of you, I have a simple message: Hold on a little longer. A better America begins tonight," he told the crowd.

The presumptive nominee faces the task of not just uniting grassroots conservatives but also coordinating hand-in-glove with Republican Party officials. Republican National Committee Chairman Reince Priebus declared Romney the "presumptive nominee" in a statement Wednesday and announced he has directed his staff to "open lines of communication with the Romney campaign."

"We will ensure that our finance, political and communications teams are fully synchronized," he said.

Romney's campaign has already erected a joint fundraising committee with the RNC looking ahead to November. The alliance allows Romney's operation to tap into the GOP's 15 battleground state teams and their staff.

The Romney campaign also has dozens of staff members dealing just with state committee officials on Republican convention planning.

Meanwhile, the campaign, which has been stuck in a chaotic primary battle for months is turning to raise money for what could be history's most expensive presidential election. President Obama enters the race with a daunting fundraising advantage, but Romney -- by far the most well-heeled candidate in the primaries -- is immediately hitting the fundraising circuit to start closing the fundraising gap with Obama.

Fox News' Carl Cameron and's Judson Berger contributed to this report.