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Associated Press
Republican presidential candidate, Texas Gov. Rick Perry during a campaign stop in Derry, N.H., Friday, Sept. 30, 2011.

WASHINGTON — Rivals Rick Perry and Mitt Romney are furiously scurrying to recruit heartbroken holdouts who had hoped GOP celebrities Chris Christie or Sarah Palin would join the Republican presidential contest.

With a slew of donors and activists now up for grabs, the leading two Republican candidates redoubled their efforts — and made personal appeals — this week to win over unaligned high-dollar and high-power GOP players in what's become largely a two-man nomination fight.

"We're at a point when the large group of undecided activists are going to choose their candidate," said Jennifer Horn, a conservative activist in New Hampshire who hasn't picked a contender. "People are starting to accept the field and accept that these are our choices. It's time to get behind someone who is a candidate, someone who is running."

Romney, who essentially has been running for president for five years, spent a chunk of the week calling fundraisers and activists anew who have long sat on the sidelines; the former Massachusetts governor hoped they would finally decide to back him. Perry, who entered the race just seven weeks ago, was working to make up quickly for lost time; the Texas governor hoped that new supporters would give his campaign a lift after a few rocky weeks.

It's not clear whether Romney or Perry have been more successful at courting Christie supporters, including Wall Street donors. And it's equally unclear where Palin supporters — many from the party's conservative and tea party wings — will end up. Many turned to social networks to blast her decision not to run for president but they also didn't indicate who they would back instead.

Of the two candidates, Perry may have the better shot at picking up Palin backers, given his links to evangelical voters and tea party activists. Those constituencies aren't a natural fit for Romney, a Mormon who has switched positions on issues social conservatives hold dear. To that end, Perry's central challenge is to convince social and religious conservatives to unite behind him in places like South Carolina and Iowa instead of splintering among other candidates like Rep. Michele Bachmann and former Sen. Rick Santorum.

To varying degrees, both Romney and Perry are in a race to get the stamp of approval from the GOP establishment, which hasn't fallen in line behind any one candidate as it searches for the strongest Republican to challenge President Barack Obama.