Almost across the board, the former governor of neighboring Massachusetts performed better in New Hampshire than he had last week in more deeply conservative Iowa, where he won by a whisker.
Romney was backed by 42 percent of New Hampshire conservatives, more than twice the share won by his nearest rival, Texas Rep. Ron Paul, and similar to the margin by which he prevailed among tea party supporters. It was almost double the portion of Iowa conservatives who had backed Romney.
New Hampshire moderates and liberals also leaned toward Romney, with 37 percent supporting him, more than any other contender.
As promising as the evening was for the winner, two of the men battling to become the conservative alternative to him performed weakly with such voters in New Hampshire.
Just 15 percent of conservatives backed former Pennsylvania Sen. Rick Santorum, who finished just a handful of votes behind Romney in Iowa last week. Former House Speaker Newt Gingrich, who has launched searing attacks against Romney, won just 13 percent of the votes of conservatives. Both men also won just over 1 in 10 tea party backers.
Despite New Hampshire's relatively low unemployment rate of 5.2 percent, 6 in 10 voters Tuesday named the economy as the issue that most determined their vote. Among them, 45 percent favored Romney, more than double the number who supported Paul.
In Iowa, just a third worried about the economy had backed Romney.
By many measures, voters looking for a November winner said Romney was the way to go.
Given four choices, over one third said the key quality they sought in a candidate Tuesday was the ability to defeat Obama. Of those voters, 62 percent picked Romney, bettering the 48 percent he received from them in Iowa.
Regardless of whom they voted for, 56 percent in New Hampshire named Romney as the GOP contender with the best shot at victory in November.
Further underscoring his wide appeal, 61 percent of voters Tuesday said they would be satisfied with Romney as the party's nominee. Majorities said they would be unhappy if Santorum, Paul or Gingrich were the nominee.
Overall, 66 percent of voters expressed satisfaction with the field of GOP contenders. In New Hampshire's 1996 GOP contest, just over half of voters said they were content with the party's candidates, while in 2000 more than 8 in 10 were satisfied.
As he did last week in finishing third in Iowa, Paul drew strength from voters under age 30 and lower-income people. He was also the strong preference for voters looking for a true conservative and a candidate with strong moral character, winning about 4 in 10 voters who were looking for each quality.
Jon Huntsman, the former Utah governor, did best among tea party opponents — an ominous sign for a candidate in a party in which that conservative bloc wields strong influence. He also shared the lead with Romney among the 1 in 4 people seeking someone with the proper experience to be president.
The exit poll showed disappointments galore for Santorum, who had high hopes after his surprisingly strong Iowa finish.
Santorum won just small fractions of the votes of Catholics and working-class people, groups he has hoped to appeal to because of his own background.
He was only able to finish about even with Romney among New Hampshire voters considering themselves very conservative and with born-again or evangelical voters. He trailed both Romney and Paul among tea party backers.
Underlining how much Santorum was relying on his strong Iowa showing to win support, 72 percent of his backers said they'd decided to vote for him in the last few days — even though these late deciders comprised less than half of those voting Tuesday.
Romney did worse among people who decided in recent days than with those who'd made their minds up earlier, but he still got more votes from both those categories than any of his rivals.
Romney was the runaway winner among voters who said they are Republicans, and finished about even with Paul among the roughly half of New Hampshire voters who call themselves independents. The large number of independent voters in New Hampshire reflects state voting rules that let unaffiliated voters participate in either party's primary.
Romney's other sources of strength included the wealthy, college graduates, older voters and people saying they had voted previously in New Hampshire's GOP primaries.
The survey was conducted for AP and the television networks by Edison Research as voters left their polling places at 40 randomly selected sites in New Hampshire. The preliminary results are based on interviews with 2,760 voters and have a margin of sampling error of plus or minus 3 percentage points.