* Perry's quick rise makes him a convenient target
* Romney in position to gain from Perry's stumbles
By John Whitesides
WASHINGTON, Sept 23 (Reuters) - Republican Rick Perry has become the punching bag, and presidential rival Mitt Romney is feeling no pain.
For a second consecutive debate, Romney prospered on Thursday as Perry came under heavy fire from campaign rivals over his views on immigration, vaccinations and the Social Security retirement program. [ID:nS1E78L26F]
Perry, the Texas governor and Republican front-runner, is everyone's favorite new target. Romney, who lost his poll lead after Perry's entry in the race last month, has sailed through largely unscathed.
"Romney is the most polished debater in the group," said Republican strategist Ford O'Connell. "Perry has not been as good, and it's hurting him."
The most recent Real Clear Politics average of polls in the Republican battle for the right to challenge President Barack Obama gives Perry a 7-point edge over Romney, 28 percent to 21 percent, with the rest of the field trailing in single digits.
But several polls show Perry's edge in the race diminishing in the last few weeks as the Republican contenders pile on the new front-runner.
On Thursday, U.S. Representative Michele Bachmann and former U.S. Senator Rick Santorum were happy to help Romney take the polish off Perry's record in Texas. As in last week's debate, Perry struggled at times to respond.
He was even booed by the debate crowd after defending his policy of allowing the children of illegal immigrants to pay in-state tuition in Texas.
"The attacks on Perry really seem to be landing right now," Republican strategist Ron Bonjean said. "Romney is better at deflecting attacks and is much more practiced in this."
After his quick rise in the polls, Perry's drift back to the pack was almost inevitable. He had no experience outside Texas politics when he jumped into the race, and his sudden success has made him an inviting target.
In contrast Romney, the former Massachusetts governor, has been running for president nearly non-stop since his unsuccessful 2008 bid. With only Perry to worry about, he has had an easier road.
After Romney and Perry renewed their clash over the future of the Social Security retirement program early in the debate, the other contenders quickly jumped in to make their own cases against Perry.
Bachmann, hoping to reclaim conservative support she has lost to Perry, called his tuition plan "madness" and said his order requiring young girls be vaccinated against a sexually transmitted virus that causes cervical cancer "gave parental rights to a big drug company."
On the tuition plan, Perry questioned the heart of anyone who would punish a child for a parent's transgression. But Romney argued they were getting preferential treatment over children from 49 other states who were legal citizens.
Santorum joined in the Perry bashing, criticizing his opposition to a border fence and demanding to know if his border policies were working.
Perry, focusing his attacks solely on Romney, renewed the flip-flopper charge frequently raised during Romney's 2008 presidential run for his evolving views on issues like abortion after he left the governor's office in liberal Massachusetts.
"I think Americans just don't know sometimes which Mitt Romney they're dealing with," Perry said. "We'll wait until tomorrow and see which Mitt Romney we're talking to tonight."
Romney still has significant difficulties of his own, most notably continued conservative suspicion of his support for a Massachusetts healthcare plan that is similar to Obama's national healthcare overhaul.
But Perry's debate performances and the tightening race could leave the door open for another candidate to get in the mix. Former Utah Governor Jon Huntsman has risen slightly in recent New Hampshire polls, and could challenge Romney there.
A sense of weakness in the two leaders also could be enough to lure a new candidate into the race.
Sarah Palin, the 2008 vice presidential candidate and Tea Party movement hero, is still pondering a late plunge. She has joined the Perry bashers recently, criticizing him on the vaccine issue.
Romney has encouraged Palin to get in the race, hoping she could be another force on the right splitting the votes of social and Tea Party fiscal conservatives with Bachmann and Perry. That would clear more room for Romney up the middle.
Romney told the USA Today newspaper it would be a "good thing" if Palin declared her candidacy. "She would make the race that much more exciting, bring more people to watch the debates, and I hope she gets in," he said. (Editing by Vicki Allen)