Washington ? Mitt Romney and Newt Gingrich’s trailing rivals derided the leading presidential contenders on Sunday as insufficiently conservative, each trying to find a second wind in the race to become the Republican nominee with time running out before voting begins.

Rep. Michele Bachmann of Minnesota combined the two leaders into a “Newt Romney” character. Rep. Ron Paul of Texas said Gingrich and Romney “come from the same mold.” Texas Gov. Rick Perry said voters aren’t looking for a fact-spewing “robot.” All attempted to claw their way back into the campaign that has suddenly become a two-man race.

“As I was studying the candidates, especially Newt Gingrich and Mitt Romney, it is very clear that there’s not a dime’s worth of difference between the two of them, because both of them have advocated for the health care mandate. In Newt Gingrich’s case for 20 years. And in Mitt Romney’s case he’s the only governor in the United States’ history to put into place socialized medicine,” Bachmann said.

Iowa’s lead-off caucuses are coming quickly. The candidates have spent months — if not years — preparing for the nominating process that starts Jan. 3. Perry spent Sunday in Iowa and planned to return Wednesday for a marathon bus tour across the state.

Gingrich and Romney, meanwhile, planned competing events on Monday in New Hampshire, where Gingrich will end the day debating former Utah Gov. Jon Huntsman, Lincoln-Douglas style. Both Gingrich and Romney planned to return to Iowa later in the week. Gingrich, Bachmann, Perry and former Sen. Rick Santorum planned to attend an event with former Arkansas Gov. Mike Huckabee on Wednesday, and all planned to participate in the campaign’s 13th debate on Thursday.

Yet the topsy-turvy race remains fluid, and the struggling candidates are hoping to deflate Romney and Gingrich by noting similarities on issues that could concern conservatives.

Romney and Gingrich at one time backed requiring individuals to purchase health insurance, although both decry the federal provision in Democrats’ health care law. Both also supported the Wall Street bailout, government subsidies for ethanol and the science suggesting humans play a role in climate change — all toxic among the party’s orthodox.

Romney, the former Massachusetts governor making his second bid for the presidency, has amassed a considerable campaign bank account and has built a formidable political machine. Gingrich, a former House speaker, has seen resurgence in polling and fundraising after a near-meltdown this summer. In short time, he has worked to build an organization but his challenge remains matching the public’s interest with the nuts and bolts of a traditional campaign.

The pair’s rivals, though, are unwilling to concede that the race is down to the two. An NBC News/Marist poll released Sunday shows Gingrich surging to more than 42 percent support to Romney’s 23 percent in South Carolina; in Florida the former speaker is favored by 44 percent of those polled, to Romney’s 29 percent. No one else in the field breaks 10 percent in either state.

With focused criticism, they’re working to cast the pair as clones and unacceptable to the party’s conservative base, which has huge sway in deciding the nomination.

Campaigning in Ames, Iowa, Perry said Romney’s past support for health care mandates should haunt him.

“He can deny it as many times as he wants,” Perry told about 150 people in a coffee shop near Iowa State University. “But that is what he thinks.”

Earlier in the day, he said voters “are looking for somebody who’s got values that are based with a deep rudder in the water.”