For Gingrich, the former House speaker, the backing builds on his recent rise in the polls and quick work to build a campaign after a disastrous start in the summer. Romney, the former Massachusetts governor who has a vacation home in the state and has been called a "nearly native son of New Hampshire," absorbed the blow heading into the Jan. 10 vote that's vital to his campaign strategy.
"We are in critical need of the innovative, forward-looking strategy and positive leadership that Gingrich has shown he is capable of providing," The New Hampshire Union Leader said in its front-page editorial, which was as much a promotion of Gingrich as a discreet rebuke of Romney.
"We don't back candidates based on popularity polls or big-shot backers. We look for conservatives of courage and conviction who are independent-minded, grounded in their core beliefs about this nation and its people, and best equipped for the job," the endorsement said.
The Union Leader's editorial telegraphed conservatives' concerns about Romney's shifts on crucial issues of abortion and gay rights were unlikely to fade. Those worries have led Romney to keep Iowa's Jan. 3 caucuses — where conservatives hold great sway — at arm's length.
At the same time, the endorsement boosts Gingrich's conservative credentials. He spent the week defending his immigration policies against accusations that they a form of amnesty. On Monday, Gingrich takes a campaign swing through South Carolina, the South's first primary state.
Even Democrats on Sunday were noting Gingrich's rise.
"He's clearly a smart guy," said Sen. Chuck Schumer, a Democrat from New York. "And look, I give him some credit for not just blowing with the winds on an issue like immigration. That showed some real courage."
Romney, taking a few days' break for the Thanksgiving holiday, has kept focused on a long-term strategy that doesn't lurch from one development to another. Last week, he picked up the backing of Sen. John Thune, a South Dakota conservative, to add to his impressive roster of supporters.
The Union Leader's rejection of Romney wasn't surprising despite his efforts to woo state leaders. The newspaper rejected Romney four years ago in favor of Arizona Sen. John McCain, using front-page columns and editorials to promote McCain and criticize Romney. In the time since, Romney courted publisher Joseph W. McQuaid. Earlier this year Romney and his wife, Ann, had dinner with the McQuaids at the Bedford Village Inn near Manchester, hoping to reset the relationship. It didn't prove enough.
Romney's advisers were quick to point out that Gingrich went into October with more than $1 million in campaign debt. Romney, meanwhile, was sitting on a pile of cash and only last week began running television ads — a luxury Gingrich can't yet afford.
The duo's rivals, meanwhile, tried to gain traction.
Herman Cain on Sunday criticized any immigration proposal that included residency or citizenship but struggled to explain how he would deal with the millions of people estimated to be currently living illegally in the United States.
Cain, who joined the race to great fanfare, has seen his luster fade as his seemed to have trouble articulating the nuances of his policy positions. For instance, he was unable to explain the difference between "targeted identification," which he says would determine common characteristics of people who want to harm the United States, and racial profiling.
At the same time, Cain acknowledged that accusations that he sexually harassed several women during his days running the National Restaurant Association in the 1990s have pulled him from among the front-runners. He has flatly denied the allegations repeatedly.
"Well, obviously false accusations and confusion about some of my positions has contributed" to his fall in the polls, Cain said.
While Romney enjoys solid support in national polls, many Republicans have shifted from candidate to candidate in search of an alternative to Romney. That led to the rise — and fall — of potential challengers such as Cain, Rep. Michele Bachmann of Minnesota and Texas Gov. Rick Perry.
Romney enjoys solid leads in New Hampshire polls, too. A poll released last week showed him with 42 percent support among likely Republican primary voters in New Hampshire. Gingrich followed with 15 percent in the WMUR-University of New Hampshire Granite State poll.
Rep. Ron Paul of Texas posted 12 percent support and former Utah Gov. Jon Huntsman found 8 percent support in that survey.
Those numbers could shift based on the backing of The Union Leader, a newspaper that proudly works to influence elections, from school boards to the White House, in the politically savvy state.
Huntsman, President Barack Obama's former ambassador to China, said the endorsement points to how competitive the New Hampshire contest is.
"A month ago for Newt Gingrich to have been in the running to capture The (New Hampshire) Union Leader endorsement would have been unthinkable," Huntsman said in an interview Sunday during a break in campaigning. "I think it reflects, more than anything else, the fluidity, the unpredictability of the race right now."
The endorsement, signed by McQuaid, suggested that New Hampshire's only state-wide newspaper was ready to assert itself again as a player in the GOP primary — even if the newspaper has reservations.
"We don't have to agree with them on every issue," McQuaid wrote in the editorial that ran the width of the front page. "We would rather back someone with whom we may sometimes disagree than one who tells us what he thinks we want to hear."
Yet with six weeks until the primary, The Union Leader's move could again shuffle the race, further boosting Gingrich and priving a steady stream of criticism against his rivals. In recent weeks, Gingrich has seen a surge in some polls as Republicans focus more closely on deciding which candidate they consider best positioned to take on Obama.
He has also started to put together a strong campaign organization.
In New Hampshire, he brought on respected tea party leader Andrew Hemingway and his team has been contacting almost 1,000 voters each day. Gingrich hasn't begun television advertising and has refused to go negative on his opponents.
The newspaper has a decidedly mixed record of picking candidates. It backed Steve Forbes in 2000 and Pat Buchanan's 1992 and 1996 bids. Neither candidate won the Republican nomination.
Gingrich, who left the House in 1999 under the cloud of an ethics investigation and after disastrous midterm elections for the GOP, has faced skepticism of his personal life. He married to his third wife and acknowledged infidelity during his first marriages.
Even so, voters are giving Gingrich a look — and the timing appears to be ideal for him.
"Romney is a very play-it-safe candidate. He doesn't want to offend everybody or anybody," said Drew Cline, the op-ed editor of The Union Leader. "He wants to be liked. He wants to try to reach out and be very safe, reach out to everybody, bring everybody on board."
That isn't the brand of candidate The Union Leader was looking to back, he said.