Rick Perry hopes to end a string of poor performances and campaign rival Mitt Romney looks to consolidate his newly regained front-runner status at a U.S. presidential debate for Republicans on Tuesday.

The debate also will be Herman Cain's first moment in the political spotlight since gaining momentum with his surprise Florida straw poll win last month, and the former pizza executive is sure to face new scrutiny.

Eight Republican contenders will participate in the debate in New Hampshire, the seventh this year in the party's race for the nomination to face President Barack Obama in 2012.

Three months before Republican voting begins, the pressure will be on Perry to reverse a streak of wobbly debate showings that put his once high-flying campaign into a nosedive.

Perry will be in the spotlight because he has to put on a better performance, said Fergus Cullen, former chairman of the New Hampshire Republican Party. The last few debates started to peel back the layers of the onion on Perry -- and he really hasn't held up well.

Perry, the Texas governor, roared past Romney to take the lead in polls after getting in the race in August. But he foundered after several stumbling debate performances where he was hammered over his immigration policies and for ordering young girls be vaccinated for a sexually transmitted virus.

Romney, the former Massachusetts governor whose 2008 White House bid failed, has retaken the lead in polls but has still not won over conservatives who remember his past support in Massachusetts for abortion rights and a healthcare mandate.

A poll released on Tuesday by NBC News and Marist College showed Romney with a commanding 30-point lead over his rivals in moderate New Hampshire and a small edge over Cain in Iowa, where social and religious conservatives play a big role. Those two states kick off voting in the nominating race in January.

Romney has been a steady performer in the debates and has gone largely untouched by his rivals, particularly in the three debates last month that focused on Perry. But Romney's strong poll numbers could make him a target this time.

'TAKING SOME RISKS'

Some of the other second-tier candidates, including former U.S. Senator Rick Santorum and former Utah Governor Jon Huntsman, also could be trying to get noticed as time runs out for them to make a move.

I'm expecting some of the second- and third-tier candidates to start finally taking some risks to distinguish themselves, Cullen said. If you're Jon Huntsman or Rick Santorum, your opportunities are starting to become numbered.

The debate begins at 8 p.m. EDT on the campus of Dartmouth College and will be carried by Bloomberg Television. It will focus on economic issues.

Candidates will sit side-by-side with the moderators in a round-table format, surrounded by the audience, in a bid to generate more interaction, sponsors said.

It is the second debate this year in New Hampshire, which is expected to hold its influential nominating contest in early January. The exact date remains uncertain as other states jockey to gain influence by jumping ahead in the calendar.

Huntsman, who has staked his campaign on a strong showing in New Hampshire, has gained slightly there in recent polls and needs a good debate performance to maintain his momentum.

Staunch social conservatives like Cain, Perry, Santorum and U.S. Representative Michele Bachmann might find New Hampshire's more moderate voters a less-receptive audience. Also participating in the debate will be Representative Ron Paul and former House of Representatives Speaker Newt Gingrich.

(Editing by Christopher Wilson and Philip Barbara)