Republican voters are down on the contenders vying to be their standard bearer against President Barack Obama, according to a poll released Monday.

More than half of Republican voters polled by the Pew Research Center -- 52 percent -- said the final four Republican presidential candidates were fair or poor, while 46 percent of the GOP rank and file gave the candidates an excellent or good rating.

Amid a bruising primary campaign, Republicans remain unimpressed with their party's presidential field, Pew said.

Before voters actually headed to the polls in New Hampshire, the Jan. 10 first-in-the-nation primary, Republicans were more upbeat about their options - 51 percent said they were excellent or good.

Of course, as the primary race continues and the field shrinks, stakes become higher and the attacks get sharper.

Former House Speaker Newt Gingrich, in the runup to his massive 13-point victory in the South Carolina primary, battered his chief rival there, Mitt Romney, with criticism over his tax returns and career running a private equity firm, Bain Capital.

Romney, to head off another loss to Gingrich in Tuesday's Florida primary, returned fire, bringing up the House of Representatives' official rebuke of Gingrich in 1997 on ethics violations -- the first speaker to be reprimanded. Gingrich has since collapsed in Florida, according to polls showing Romney, a former Massachusetts governor, with a wide lead.

Meanwhile, Rep. Ron Paul of Texas and former Sen. Rick Santorum of Pennsylvania are staying out of Florida primary and are campaigning elsewhere, away from the media's focus on the Romney-Gingrich battle in the Sunshine State.

Monday's Pew poll surveyed 1,006 adults, including 341 Republican and GOP-leaning voters, from Jan. 26 to 29.