DES MOINES, Iowa - With Christmas out of the way, the battle for the Republican presidential nomination resumed with gusto Tuesday, a still-wide-open race meaning a frantic dash in the final week before Iowa kicks off the voting Jan. 3.

Candidates poured back into Iowa, with Michele Bachmann, Rick Perry, Mitt Romney, and Newt Gingrich all launching statewide bus tours, joining Rick Santorum, who returned Monday. Ron Paul is scheduled to arrive Wednesday.

Ads returned to Iowa TV channels, restarting an air war that has cost an estimated $10 million, much of it spent on attacking onetime front-runner Gingrich, the former House speaker, as a flip-flopper who once backed liberal causes and a Washington insider who cashed in after leaving public office.

As they raced toward the voting, Romney, the former Massachusetts governor, signaled confidence that he will eventually win the nomination even if he doesn't win Iowa. Gingrich awoke to another challenge, with a report that he had praised Romney's Massachusetts health-care law, which is deeply unpopular with conservatives.

Before arriving in Iowa on Tuesday evening, Romney swung through his stronghold of New Hampshire, which holds its primary a week after Iowa's precinct caucuses.

"I'm not exactly sure how all this is going to work, but I think I'm going to get the nomination if we do our job right," Romney said there.

Romney worked to lower expectations in Iowa, a state he wooed and lost in 2008.

"What I know I have to do is get about 1,150 delegates, and that's going to take time in a lot of states, and I hope to get off to a good start," he said later Tuesday.

Romney poked fun at Gingrich for failing to qualify for the primary ballot in Virginia and for likening that setback to the Japanese attack on Pearl Harbor.

"I think it's more like Lucille Ball and the chocolate factory," Romney said, referring to the classic 1952 sitcom scene in which Ball's character can't keep up with a candy assembly line.

Perry, the Texas governor, also failed to qualify in Virginia, and his campaign filed suit Tuesday in federal court there over the exclusion.

Gingrich faced more potential bad news with a Wall Street Journal report that his consulting company published a newsletter in 2006 lauding Romney's health-care law as "the most interesting effort to solve the uninsured problem in America today."

The state law includes a mandate that people buy insurance, and many Republicans now revile it as a model for the national law that President Obama and congressional Democrats pushed through last year.

All of it pointed to a wide-open finish next week, with Texas Rep. Paul also among the top-tier candidates, and with Perry, Minnesota Rep. Bachmann, and former Pennsylvania Sen. Santorum working overtime for a last-minute surge that would propel them into the top three finishers.

"It's just as fluid now as it's been for weeks," said Timothy Hagle, an associate professor of political science at the University of Iowa.

The candidates have spent an estimated $10 million this month in ads in the state. Perry reportedly has spent $2.86 million, followed closely by Restore Our Future, an independent group promoting Romney.

Paul faced new questions, with reports that a newsletter he published had regularly printed racist and anti-Semitic remarks. Paul says he didn't know what was in the newsletters.

Santorum looked for a boost from the state's sizable evangelical Christian community.

"Enthusiasm and organization usually equal turnout," said Dennis Goldford, a professor of politics and international relations at Drake University in Des Moines. "And their people are enthusiastic."