Republican Presidential Candidates Trade Attacks In GOP Debate (VIDEO)

SIMI VALLEY, Calif. -- Quick to tangle, Republican presidential rivals Rick Perry and Mitt Romney sparred vigorously over job creation and Social Security Wednesday night in a feisty campaign debate that marked a contentious new turn in the race to pick a 2012 challenger to President Barack Obama.

Far more than in earlier GOP debates this summer, the candidates mixed it up in their first faceoff since Perry entered the race and almost instantly overtook Romney as front-runner in opinion polls. Those two - as well as other contenders on stage - sniped at one another, contradicted allegations and interrupted media questioners to demand opportunities to take each other on.

"Michael Dukakis created jobs three times faster than you did, Mitt," Perry jabbed in the debate's opening moments, referring to one of Romney's Democratic predecessors as governor of Massachusetts.

"As a matter of fact, George Bush and his predecessors created jobs at a faster rate than you did," Romney shot back at Perry, the 10-year incumbent Texas governor.

The debate was the first of three in as many weeks, at a time when the economy is struggling, unemployment is seemingly stuck at 9.1 percent and Obama's popularity is sinking in the polls - all events that could make the GOP nomination worth more than it appeared only a few months ago.

Perry and Romney stood next to each other on the debate stage at the Ronald Reagan Presidential Library, a setting that invoked the memory of the conservative Republican who swept to two terms as president. And for much of the evening, the two men were at the center of the action, largely reducing their rivals to the roles of spectators looking for a way into the action.