WASHINGTON — Sen. Barack Obama owned it after winning in Iowa. Sen. Hillary Rodham Clinton stripped it away in New Hampshire, and Obama grabbed it back in South Carolina.
She took it again with a strong performance on Super Tuesday but didn't hold it for long: Obama won 11 straight contests in February. He began making the case to Democratic voters and party leaders that his obvious momentum made him the best choice to be the Democratic nominee for president.
Then came Clinton's victories in Texas and Ohio on Tuesday night, padded by her win in Rhode Island.
In the eight weeks since the Iowa caucus, momentum — the most magical term in the political lexicon — has behaved more like a greased pig than a Holy Grail.
Now, with seven long weeks before the next significant primary, in Pennsylvania on April 22, Clinton faces the difficult task of maintaining whatever momentum she has gained.
"We had what might be characterized as a dry spell prior to last night," Harold Ickes, a top Clinton adviser, said Wednesday. "We think that we have turned the corner in the campaign."
Political scientists and campaign operatives say the seesaw of the Democratic race has upended what they thought they knew about momentum. Of the 370 delegates at stake Tuesday, Clinton enjoyed a net gain of only 12, according to the Associated Press count, hardly denting Obama's lead in the race for the 2,025 delegates needed to secure the nomination.
Also, Obama is expected to cut into Clinton's recent gains this Saturday in Wyoming and on Tuesday in Mississippi.
"You kind of have to pause and see if (Tuesday) was an aberration or a start of a new pattern. Unfortunately, four states do not a pattern make," said Jennifer Duffy, editor of the nonpartisan Cook Political Report. "I think we've learned this cycle that the rules don't apply — everything that we've learned, everything we've taught in presidential primaries is not helpful."
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Before Tuesday, Patrick Kenney believed momentum still mattered. Then Obama lost three out of four contests after winning the previous 11.
"This year does not fit our traditional view of momentum, being that once one candidate got on a roll, they would build momentum and people would switch to them, just to get on the bandwagon," said Kenney, chairman of the political science department at Arizona State University and author of several studies on political momentum.
"People get on the bandwagon because other candidates start to fade. But she's not fading. She's in there all the time, fighting."
The idea is that whoever is winning is likely to keep winning, and political people tend to bet on winners in the form of donations and endorsements.
Experts say this year's distortion is the product of several factors. Both candidates are well-known, well-organized and well-funded, so neither has been able to overwhelm the other. The Democratic Party's nominating process, too, awards delegates based on the proportion of the vote, so even the loser gains delegates.
Finally, supporters of each candidate tend to like the other.
"Whenever someone seems to be on the roll, the voters really insert themselves in the process," said veteran consultant Chris Lehane, who supports Clinton but isn't involved in her campaign. "It's a function of the fact that on the Democratic side, voters like both candidates an awful lot, and I think you've seen that as the voters go back and forth in trying to make their decisions."
Both campaigns are wary of being seen as overly aggressive toward their opponent, but the fight could get nastier. Clinton ran aggressive advertisements against Obama in Texas and Ohio, including one that said voters will want Clinton, not him, when the phone in the White House rings for a crisis at 3 a.m.
Costas Panagopoulos, director of the Center for Electoral Politics and Democracy at Fordham University in New York, said Clinton put Obama on the defensive, and it apparently worked. Obama should expect more.
"He can't adopt a cavalier approach and brush off her criticism for too long," Panagopoulos, said. "He's trying to take the high road, but if he doesn't want her criticism to penetrate the consciousness of the electorate, he has to come off of his high horse and defend himself. That has the potential to get very dirty."
The Obama campaign suggested the candidate will go on the offensive. Speaking Wednesday on CNN, Obama offered a sample of what's to come as he challenged Clinton's assertions that she is more experienced.
"Well, she's yet to cite what experience, in fact, prepares her for that 3 a.m. phone call," Obama said. "When her advisers were asked about it, there was a deafening silence. So it was a clever ad, but the bottom line is that the most important foreign policy call that she's had to make since she's been in public office was whether or not to follow George Bush into Iraq. And she made the wrong decision."
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With no major contests until Pennsylvania, the campaigns will be struggling to give themselves a boost by touting strong fundraising numbers and announcing key endorsements.
They'll also be heavily courting the 796 superdelegates — party officials and leaders — who can support either one and ultimately may decide the nominee.
Clinton will continue to remind superdelegates and voters that she has won the big states, including California and her home state of New York.
"The last word in the primary was last night, when she won three out of four," said Rep. Debbie Wasserman Schultz, a Broward County Democrat and leading Clinton supporter in Florida.
"The one who has the last wave of momentum will be able to ride that wave through the next series of primaries. She took away Barack Obama's ability to say, 'I won 11 straight.' "
Wes Allison can be reached at