Republican presidential candidates former Massachusetts Gov. Mitt Romney, left, and former Speaker of the House Newt Gingrich, right, talk during a break in the Republican debate, Saturday, Dec. 10, 2011, in Des Moines, Iowa. Attacked as a lifelong Washington insider, Gingrich parried criticism from Mitt Romney Saturday night, telling the former Massachusetts governor,

WASHINGTON (AP) — Mitt Romney and Newt Gingrich's trailing rivals derided the leading GOP presidential contenders as insufficiently conservative in hopes of regaining momentum in the race.

Minnesota Rep. Michele Bachmann again combined the two into a "Newt Romney" character during a Sunday interview. Texas Gov. Rick Perry says voters aren't looking for a fact-spewing "robot." And Rep. Ron Paul says Gingrich and Romney "come from the same mold."

All are attempting to claw their way back into the campaign that suddenly has become a two-man race.

Iowa's lead-off caucuses are coming quickly, with the Jan. 3 start to a nominating process the candidates have spent months preparing for. Yet the race remains fluid, and the candidates are hoping to deflate Romney and Gingrich by noting similarities that could concern conservatives.

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