Super Tuesday may not do to Mitt Romney's opponents what it did to him four years ago. Namely, force them to drop out.
Voters in 10 states, stretching from Massachusetts to Alaska, are participating in GOP presidential primaries and caucuses on Tuesday.
Polls closed in three states at 7 p.m. ET, and former House Speaker Newt Gingrich has won Georgia, The Associated Press projects.
Romney entered the day with considerable momentum, having won the last five contests in a row. Former Pennsylvania Sen. Rick Santorum, who has served as Romney's main competition over the past month, has been slipping in the polls in the most contentious battleground states.
Romney is thus expected to take at least a plurality of the contests being held on Tuesday and perhaps half of the 419 delegates at stake based purely on Tuesday voting. The additional 18 delegates are state and national party officials who will attend the convention as unpledged delegates.
But that still may not be enough to deal his remaining opponents the kind of knockout blow he suffered during the last campaign.
In 2008, Romney lost 13 primaries on Super Tuesday, prevailing only in Massachusetts — where he had served as governor earlier in the decade — and heavily Mormon Utah. He performed better in caucuses held that night, but his losses were so great that he dropped out of the race two days later.
All four major GOP candidates, though, have a chance at winning at least one state on Tuesday — which in turn would give them continuing impetus to keep up the fight.
"Here's the question: Does Romney get more than the other three guys combined?" says Peter Brown, assistant director of the Quinnipiac University Polling Institute. "If he can't get above 50 percent of the delegates, we're going to have this long, slow trek to Tampa," which will host the GOP national convention in August.
That's what makes Super Tuesday so crucial. It could either place Romney securely in the driver's seat, or keep the GOP contest what it's been for months — a hard and often unpredictable slog.
"I can still see how Romney can lose, but I can't see how any of these other guys can win," former presidential adviser David Gergen said on public radio's On Point.
The Michigan Playbook
Thanks in part to his momentum — and heavy spending on negative advertising — Romney has been climbing up in the latest polls in the two states that are considered most competitive on Tuesday, Ohio and Tennessee.
If he carries both of those states, he will certainly be cast as the dominant front-runner for the Republican nomination.
Romney is expected to win Massachusetts and neighboring Vermont, and is virtually assured of victory in Virginia, where Santorum and Gingrich failed to qualify for the ballot.
"The big thing is that people are looking at [Romney] and coming to the conclusion that he's the only one that has the chance to beat [President] Obama," says Richard Finan, former president of the Ohio state Senate. "They look at Santorum and think, 'He might be a good guy, but I don't think he can beat Obama,' and I think that way, too."
Romney is hoping to repeat a strategy that was successful for him last week in Michigan — erase Santorum's early polling lead through relentless negative advertising funded by his own campaign and by Restore Our Future, the superPAC backing his candidacy.
"He spent, what, $12 million in the last two weeks on pretty much all negative advertising," says Dale Fellows, who chairs the Lake County GOP, just east of Cleveland, and supports Santorum. "It's pretty overwhelming."
The End Of Santorum's Surge?
Despite Romney's money advantage, Fellows notes that the latest polls show that Ohio is still a dead heat.
"We have very loyal folks, and they're out trying to convince people all the way up to the 11th hour that Rick Santorum is the guy that needs to lead the country," Fellows says.
But Santorum has no cushion left in what was once a sizable polling lead in the state. The same is true in Tennessee, which has turned into a three-man jump ball among Santorum, Romney and Gingrich.
Santorum is expected to win Oklahoma, but he may need a stronger showing than that to remain a challenger capable of putting a fright into Romney.
In addition to castigating Santorum as an earmark-happy Washington insider, Romney and his followers have knocked Santorum for failing to make the ballot in Virginia or qualify delegates in three Ohio congressional districts, pointing to these organizational failures as proof he's not sufficiently prepared to be president.
"The important things for Sen. Santorum are Ohio and Tennessee," says Mark Wrighton, a political scientist at the University of Southern Mississippi.
"If he loses both, that's close to a knockout blow," Wrighton says. "Concentrating on Iowa and New Hampshire is important, but there are other states with other ballots, and you've got to work them as hard as you can."
Possible Win For Paul
Gingrich won Georgia, which he represented for two decades in Congress. His final margin of victory there — and his performance in the other Southern states — will determine his continuing viability, suggests Charles Bullock, a University of Georgia political scientist.
"Does he carry Georgia with 35 or 38 percent of the vote?" Bullock asks. "That's not very impressive. The question is whether he can get to 50 percent."
As has been true throughout the campaign, Texas Rep. Ron Paul has concentrated most of his effort in states holding caucuses, which have lower participation rates than primaries and give more of a chance to candidates with limited but ardent support.
Idaho, North Dakota and Alaska will each be holding caucuses. Paul could nip Romney in either of the latter two states.
"Paul has actually done pretty well in Idaho before," says Gary Moncrief, a political scientist at Boise State University. "I expect him to do extremely well in the northern part of the state, which is pretty libertarian."