WASHINGTON (AP) -- If polls show one thing with certainty, it's that Republicans aren't sold on Mitt Romney and they've been looking for other presidential candidates.

At least eight other Republicans have seen their standings soar in GOP primary surveys since the beginning of the year.

Sarah Palin, Chris Christie, Mike Huckabee and Rudy Giuliani didn't run. Nor did Donald Trump. And among those who actually got in the race, Michele Bachmann, Rick Perry, and now, Herman Cain all have sat near- or at - the top of national polls, at least briefly.

The indecisiveness is a reflection on Romney, who hasn't been able to lock up the GOP's support even though he's essentially been running for president since losing his 2008 bid.

Many Republicans know him. They just don't love him.

A recent Associated Press-GfK poll found that 64 percent of conservative Republicans viewed Romney favorably but only 20 percent had deeply positive opinions about him.

"The GOP is in a rebellious and ultraconservative mood," said Andrew Kohut, president of the Pew Research Center. "And," he added, "Mitt Romney is not rebellious."

Or, for that matter, ultraconservative.

Consider that in a Tuesday debate, Romney defended the 2008-2009 Wall Street bailout that irks the tea party and declared that he could work with "good" Democrats. He also gave one of his most spirited defenses of his health care initiative when he was Massachusetts governor, legislation that President Barack Obama has called a partial blueprint for his own national overhaul.

While those positions may make him appealing to a wider swath of Americans in next fall's election, they greatly disturb conservatives who dominate the GOP primary electorate.

And that helps explain why some Republicans have been itching for someone else.

Generally, Republicans say that Romney has more experience and a better chance to beat Obama next fall than anyone else in the field. But those on the party's right flank doubt whether he - more so than other candidates - shares their values.

Conservatives in the potential Republican electorate were deeply divided on that question in a CBS News/New York Times poll early this month. Only 12 percent chose Romney, while nearly half picked Cain (20 percent), Bachmann (18 percent) or Perry (11 percent).

Such divisions have been the most defining factor of the race so far.

It's not just Romney who has failed to solidify his support with the Republican primary electorate. None of the other candidates who have risen in polls has been able to, either.

Until now, Republicans have been bouncing from candidate to candidate - and even some noncandidates - in search of the perfect nominee.

But with the GOP field set and no more people flirting with bids, it's entirely possible that Republicans will rally behind one candidate - perhaps even Romney - between now and January when the first votes are cast.

Indeed, a host of Republicans - 76 percent in a recent CBS-New York Times poll - said it was too early to say who they would support when voting begins in January. Just 19 percent said they had firmly chosen a candidate.

The volatile race is taking place in a dramatically different Republican Party than the one that nominated John McCain - and for much of the 2008 race strongly favored the thrice-married Giuliani.

The GOP fell out of public favor following McCain's loss to Obama. It then rebounded with the growth of the tea party movement, which helped Republicans win control of the House and boost its ranks in the Senate last year.

Today's Republican Party is more conservative.

"The most visible shift in the political landscape since ... 2005 is the emergence of a single bloc of across-the-board conservatives," the Pew Center said earlier this year.

And those conservatives - at least at this point - seem reluctant to continue a trend that's been the hallmark of Republican presidential primaries in recent decades.

The Republican Party usually has chosen a nominee who has been the perceived next in line.

Ronald Reagan lost once before winning the 1980 nomination. George H.W. Bush got beat that year, became Reagan's vice president and won the GOP nod in 1988. Bob Dole lost twice before becoming the party favorite in 1996. And McCain made a strong run at the nomination in 2000 before clinching it eight years later.

This year, it's Romney who is making his second bid.

And, if history is a guide, he's the most likely to end up winning the nomination - even if the all-over-the-map polls don't show it.

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Agiesta is deputy polling director for The Associated Press. Follow her at http://twitter.com/JennAgiesta

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