WASHINGTON – Mitt Romney’s and Newt Gingrich’s trailing rivals derided the leading presidential contenders 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, which 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 bus tour across the state.

Gingrich and Romney, meanwhile, planned competing events today 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 ex-Sen. Rick Santorum planned to attend an event Wednesday with ex-Arkansas Gov. Mike Huckabee, and all planned to participate in the campaign’s 13th debate Thursday.

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. He’s worked to build an organization in a short time, but his challenge remains matching the public’s interest with a traditional campaign’s nuts and bolts.

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, Gingrich 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, “I am consistent in my conservative values. I have been consistent. And Americans are looking for someone who is going to make the right decisions, not someone who can either read a teleprompter perfectly or spit out by memory a list of names.”

Perry’s comments hinted at his own stumbles. Last week, he confused Iraq and Iran during a campaign stop in South Carolina. He later said there were eight members of the nine-justice Supreme Court and mangled Justice Sonia Sotomayor’s name during an interview with The Des Moines Register.

Similarly, Paul has struggled to find footing despite legions of loyal supporters. The libertarian-leaning favorite of a hardcore slice of the electorate, Paul has aggressively challenged Gingrich over “hypocrisy” in ads running in Iowa.

And former Utah Gov. Jon Huntsman said Republicans should take another look at everyone’s record.

“People are shopping. They are listening very, very carefully,” he said.

Yet there are roughly three weeks until Iowa’s caucuses, and much can change in a race that has been remarkably fluid.