* After Gingrich's rise, a choice for Romney
* Rising concern in former Mass. governor's campaign
* Former House speaker still faces big challenges
By Steve Holland and Sam Youngman
WASHINGTON, Dec 7 (Reuters) - Is it time for Mitt Romney to come up with a new plan?
For months, the initial frontrunner in the race for the Republican nomination for president has sought to overwhelm his opponents. Romney, a former Massachusetts governor, has won waves of endorsements from party leaders, raised more than $32 million, and shown a knack for avoiding confrontations.
Then came Newt Gingrich's surprising burst to the top of the polls, fueled by his appeal to conservatives whose votes are crucial to the eventual winner of the Republican contest.
Now - after a year of campaigning and endless polls, Republican candidates get their first official chance to test their popularity with voters. Iowa kicks off the party's nominating process in January - and Gingrich's recent rise has brought Romney's campaign its first crisis.
Romney has a choice to make, analysts say: Continue his focus on beating President Barack Obama in November and hope Gingrich stumbles along the way; start directly attacking Gingrich, or employ some combination of both.
Romney's decision could define the Republican campaign for months to come.
Sources close to his campaign said there is an internal debate over how to respond to the surge by the former House of Representatives speaker, who has a double-digit percentage point lead in Iowa.
"They do not want to go at Newt directly," said a close adviser to Romney's campaign who asked not to be identified.
"Romney and Gingrich actually have a very good personal relationship, and they are aware of the fact that Gingrich is an effective attack politician. So they don't want to make him any angrier than necessary. But to the extent that (Romney) surrogates are willing to take him on, that's to be encouraged."
The adviser was not sure whether Romney - whose typical manner is one of cool detachment - could lead an effective attack on Gingrich.
"I personally question whether Romney as the attack dog against someone else in the party really would work for him," the adviser said.
ROMNEY TAKING OFF THE GLOVES?
This week, Romney signaled that he would be more aggressive.
Romney, who twice during the past week has complained about his treatment from reporters, agreed to appear on a Sunday television talk show for the first time in more than a year - "Fox News Sunday," on Dec. 18.
"You're going to see me on a lot more shows than I've been on in the last several months," Romney said during a campaign stop in Arizona.
Romney also told Fox News' Neil Cavuto that he would try to draw a contrast between himself and Gingrich.
"I will not be quiet," Romney said. He added that he and Gingrich have "very different life experiences."
That comment indicated that the nuanced jabs that Romney's campaign occasionally has thrown at Gingrich are likely to continue.
Last week, Romney sent his 36-year-old son, Josh, to campaign in Iowa just before the Sunday Parade magazine ran a friendly interview with Romney, 64, and his wife of 42 years, Ann. The Romneys also are featured in a TV ad that began running in Iowa on Wednesday.
The implied message to conservative Republican voters: Compare Romney's stable family life to the more turbulent one of Gingrich, who is in his third marriage.
So far, Gingrich, 68, has countered Romney's veiled criticisms with what have amounted to backhanded compliments.
Gingrich has called Romney likable and smart, but wondered whether a "moderate Republican" such as Romney is conservative enough to win the nomination.
GINGRICH FACES HURDLES
The Romney campaign - methodical, well-organized and heavily scripted - contrasts with Gingrich's unconventional, shoestring approach. Gingrich has leaned more on free appearances on television talk shows and interviews, than traveling to smaller meetings with voters.
Six months ago, Gingrich's campaign seemed to be going nowhere and key staff members quit after questioning his commitment to the race.
But Gingrich's chances have of winning the nomination have soared as other would-be contenders -- namely Herman Cain and Texas Governor Rick Perry -- fizzled, and he has performed well in televised debates.
He still faces major challenges: He is scrambling to raise money to keep airing TV ads, and he won't be on the primary ballots in some states -- such as Missouri -- because his campaign did not meet deadlines for collecting voters' signatures on petitions.
For now, Gingrich's campaign relies heavily on social media such as Twitter and Facebook to advertise TV interviews and stay connected with his supporters.
Winning the Iowa caucuses on Jan. 3 could give Gingrich enough momentum to challenge Romney in New Hampshire's Jan. 10 primary. Romney has double-digit leads in polls there.
But Gingrich is ahead in South Carolina for its Jan. 21 primary.
A RISKY STRATEGY
Gingrich's record in Washington, where he has been known as both a creative problem-solver and an occasionally reckless self-promoter, would seem to be prime for Romney's attack.
In 1997 he was reprimanded by the House for ethical wrongdoing and penalized $300,000. Then, after Republicans made a poor showing in the 1998 congressional elections, he resigned from the speakership and from his seat in the House.
In the years since, he has made millions of dollars as a consultant for firms seeking to do business with the government.
Romney, to this point, has focused largely on bashing Obama's leadership on the U.S. economy.
However, his campaign has begun sending a popular surrogate, New Jersey Governor Chris Christie, to South Carolina, Florida and Iowa.
Christie has questioned Gingrich's work as a legislator while emphasizing Romney's background in business.
"Gingrich has never run anything," Christie said last week in West Palm Beach, Florida.
Romney himself gently has raised questions about Gingrich, saying in New Hampshire on Saturday that he was not sure "America needs better lobbyists or better dealmakers, better insiders."
Gingrich, meanwhile, is relishing the role of frontrunner and seems to be trying to assure Republican voters that his longshot campaign really can defeat Romney's.
As was the case in his Washington days, Gingrich is prone to hyperbole: He has referred to himself as a celebrity, and compared his political comeback with Sam Walton's creation of Wal-Mart and Ray Kroc's development of McDonald's restaurants.
The way Gingrich has built momentum for his small campaign -- through televised appearances and interviews aimed at national audiences, rather than voters in specific states -- carries some risk, analysts say.
Doug Gross, a Republican from Des Moines who was chairman of Romney's Iowa campaign in 2008, said the question for Gingrich's team is, "Can they translate popularity at the national level into actual turnout at the caucuses on a cold January night?"
Gingrich's Iowa headquarters opened on Nov. 30 and has five staff members. Romney has not competed as heavily in Iowa as his rivals; his staff is about the same size.
"Our ground game is a little behind," said Gingrich spokesman R. C. Hammond. "But what we lack in time we'll make up with intensity and intelligence."
Gross, who has not endorsed anyone this time, said Romney will have to "put some serious nicks on Newt's image."
To do that, Gross said, "I think Romney's going to have to engage Newt directly."