Mitt Romney hugs his wife, Ann, as he arrived at his Super Tuesday rally in Boston. Romney narrowly beat Santorum in Ohio.
Rick Santorum and his wife, Karen, arrive at a rally in Steubenville, Ohio.
Mitt Romney shakes hands with supporters at his primary election night rally in Boston. Romney won the race in Massachusetts.
Rick Santorum supporters stand outside a primary party in Steubenville, Ohio.
Newt Gingrich and his wife, Callista, wave to supporters at an event in Atlanta after he was declared the winner of the Georgia primary.
Alex Wong/Getty Images
William House waits for Newt Gingrich to arrive during a campaign stop at the U.S. Space and Rocket Center in Huntsville, Ala.
Romney supporters celebrate during a primary night gathering on Tuesday in Boston.
Justin Sullivan/Getty Images
Romney and his wife, Ann, wave to supporters after voting in the Massachusetts primary in Belmont, Mass.
Former House Speaker Newt Gingrich speaks at the U.S. Space and Rocket Center, in Huntsville, Ala.
Sophia Walsh, 5, watches as her father, William Walsh, fills out his ballot in Steubenville, Ohio.
Joe Raedle/Getty Images
Ron Paul speaks to a crowd at the Nampa Civic Center in Nampa, Idaho. Paul is expected to do well in the Idaho primary.
Katherine Jones/Idaho Statesman/MCT/Landov
A voter casts his ballot in Montpelier, Vt. Romney is also expected to do well in the state, which borders Massachusetts.
Former Pennsylvania Sen. Rick Santorum steps off the trail to speak to the American Israel Policy Affairs Committee in Washington.
Chip Somodevilla/Getty Images
Workers hang an American flag in preparation for Santorum's election night party at Steubenville High School in Steubenville, Ohio.
Super Tuesday was an almost perfect reflection of the Republican presidential primary process so far this year.
Mitt Romney won the most states and built up a solid lead in delegates. Yet he was forced to vastly outspend his nearest rival to win the most important contest — Ohio, where he narrowly defeated Rick Santorum.
Romney won five other states, but Santorum captured three, and former House Speaker Newt Gingrich won one.
It's been this way for Romney all year. With a potentially game-changing contest on the line, Romney has always found a way to win.
"I'm not going to let you down," Romney told supporters in Boston. "I'm going to get this nomination."
Yet even as Romney once again deprived his rivals of an upset opportunity, the fashion in which he won was not entirely convincing.
Exit polls showed that many Republican voters are still not happy with their choice of candidates. And as the primary season has dragged on, with Romney winning with a strategy of persistently attacking his opponents through negative advertising, the GOP front-runner's own disapproval ratings continue to climb.
"Republicans everywhere, but particularly in the South, are not happy that Romney is going to be the nominee," says Anthony Nownes, a political scientist at the University of Tennessee.
Where Romney Won
Romney was behind in the Ohio count for much of the night, but late results from the state's largest metropolitan areas put him over the top.
He needed the win. His other victories would very likely have been dismissed as "gimmes."
Romney won Massachusetts, where he served as governor, and neighboring Vermont. He also carried Virginia, where Newt Gingrich and Santorum, a former Pennsylvania senator, failed to qualify for the ballot.
Romney also prevailed in caucus states of Idaho and Alaska.
But Romney lost all three contested races in the South, with Santorum taking Tennessee and Oklahoma (as well as the North Dakota caucuses) and Gingrich winning Georgia, which he represented in Congress for 20 years.
That doesn't bode well for Romney next Tuesday, when Alabama and Mississippi are set to vote.
Santorum may also do well in Kansas, which holds caucuses on Saturday, and Missouri, where Republicans will caucus on March 17. Santorum won a nonbinding primary in Missouri last month.
"Even though Mitt [won] Ohio, he's winning ugly," says Henry Olsen, vice president of the American Enterprise Institute, a conservative think tank. "He'll lose Saturday's Kansas caucus big, then get trounced in Alabama and Mississippi."
Speaking in Steubenville, Ohio, on Tuesday night, Santorum said: "We're going to win a few; we're going to lose a few. But at least as it looks right now, we're going to win at least a couple of gold medals and a whole passel of silver medals."
Romney Passing Tests
Santorum has presented Romney with his greatest challenges over the past month of campaigning. But Santorum has been unable to achieve the breakthrough win that could topple Romney.
Exit polls in Ohio suggest that Romney and Santorum split the conservative vote — Santorum's major source of strength in other states.
Romney also enjoyed big advantages among voters who made their picks late and who based their choices on their sense of which candidate had the best chance of beating President Obama in the fall. Romney enjoyed roughly 2-to-1 advantages among both groups.
Romney's ability to win over late-deciding voters repeated his success among similarly uncommitted voters in Michigan last week and Florida in January — attesting to his advantages in organizational strength and millions of dollars devoted to television advertising and robocalls.
"In past polls, we found that when Romney was trailing, conservatives were wary of him, but in the end enough of them seemed to be coming home," says Peter Brown, assistant director of the Quinnipiac University Polling Institute. "Americans, whether Democrats or Republicans, like being with a winner."
Only In Horseshoes
Santorum repeated his charge that Romney would be vulnerable against President Obama because of the similarity of health care laws they have championed.
He cast himself as the underdog in the race, able to carry states despite being outspent in all of them by Romney.
Listen to NPR's live special coverage of the Super Tuesday contests:
But Santorum's loss in Ohio will be interpreted as a sign, following his similar disappointment in Michigan last week, that he isn't quite strong enough of a challenger to deny Romney the ultimate prize of the nomination.
Still, Romney's inability to win among many of the GOP's most important voting blocs remains troubling to some Republican observers. Not only did he lose more states in the Deep South, but he once again trailed badly among evangelical voters even outside the South, according to exit polls.
Among those participating in Tuesday's primaries, a majority of voters expressed reservations about the person they had voted for or said they had cast their ballots strictly in opposition to an even less satisfying candidate.
Only in Georgia and Oklahoma did most voters say they strongly favored their own choices.
Poloy House told the Nashville Tennessean that he had voted for Romney solely because he felt he had the best chance of beating Obama. "I'm sick of all of them," House said.
Not A Two-Man Race
Dissatisfaction with their choices has been the dominant theme among the Republican electorate for months now. One hopeful after another has emerged as the new front-runner, only to end up having a glass jaw.
Many of those who remain opposed to Romney have pinned their hopes on Santorum, who has served as Romney's main challenger over the past month.
"The results of Super Tuesday make it more clear that Rick Santorum has become the conservative alternative to Mitt Romney," says John Stemberger, chairman of the Florida Family Action PAC, a social-conservative group, and a Santorum supporter.
Stemberger says that Gingrich's race in his political home state of Georgia was "hollow" and he should drop out, as his continuing candidacy will only help Romney.
But Gingrich made it clear in his election-night speech that he has no intention of withdrawing.
"You'll have the establishment wanting to call it to a halt, but I'm not sure Santorum and Gingrich will agree, given their victories tonight," says Tom Ingram, a Republican consultant in Tennessee.
"I think Romney will pull it out in the end," Ingram says, "but I think they'll slog it out further."