Can Clinton slow Obama-mentum?

She faces heavy pressure in Texas and Ohio primaries.

Voters in Ohio and Texas hold the future of the presidential race in their hands.

On the latest Super Tuesday, March 4, if Hillary Rodham Clinton is able to win both states and slow Barack Obama's momentum toward the Democratic nomination, she will live to fight another day. The next big showdown will be April 22 in Pennsylvania.

If Senator Obama wins Ohio and Texas, Senator Clinton will be hard put to keep going. Already, the pressure on her to drop out in that case is fierce, as Democratic elders yearn to settle on a nominee and focus on likely Republican nominee Sen. John McCain.

The nightmare scenario for the Democrats is a mixed result – say, Obama wins Texas and Clinton wins Ohio – allowing Clinton to claim another big-state victory and aim for Pennsylvania, which is demographically similar to Ohio. Because the Democrats allocate delegates proportionally, narrow victories by Clinton in either or both of Tuesday's big states will do little to help her make up her deficit in the delegate sweepstakes. But she and her campaign have indicated that she'll press on.

"Hillary being Hillary, she'll try to stay in," says Bruce Buchanan, a political scientist at the University of Texas, Austin.

Two small states also vote on Tuesday, Rhode Island and Vermont. Polls show Clinton leading in Rhode Island and Obama ahead in Vermont. But the spotlight is on the big-delegate states. Overall, Obama leads Clinton in delegates, 1,385 to 1,276, according to the Associated Press. A total of 2,025 is needed to secure the nomination.

But among "pledged" delegates – those earned through primaries and caucuses – Obama leads 1,187 to 1,035.5. The other delegates, or superdelegates, make up the difference, and party elders have also made clear that overturning a pledged-delegate victory with superdelegates would be disastrous for the party. But in the past few weeks, Obama has closed the gap in superdelegates, now trailing Clinton by just 45.

In an interview on ABC's "Good Morning America" Monday, Obama made clear he thinks it's time to end the Democratic nomination battle – and suggested that he doesn't need to win Texas and Ohio, just "do well."

"If we do well in Texas and Ohio, I think the math is such where it's going to be hard for her to win the nomination, and they'll have to make a decision about how much longer they want to pursue it," the Illinois senator said.

In a Monday morning conference call, top aides to Clinton asserted that she has regained momentum in the race and that voters are gravitating toward her message that she's more prepared than Obama to be commander in chief and to deal with a difficult economy.

"I think we've seen a tipping point and change in the momentum in the last week; I think that momentum is tipping to Senator Clinton," said strategist Mark Penn.

Polls show Texas in a dead heat and Clinton with a slight lead in Ohio. Texas's unique "two step" system for awarding delegates – first a primary (126 delegates), then a caucus (67 delegates) – may give Obama an advantage in that state. Obama has won nearly all the caucuses so far, a tribute to his campaign's organization. Texas's large Hispanic population works to Clinton's benefit, but the state's system of awarding primary delegates could minimize that advantage. Delegates are awarded according to how many votes a state Senate district gave to Democrats in the past two elections. Because black voters have higher turnout than Hispanic voters, Obama is likely to earn more delegates from his large black support than Clinton is from her Hispanic supporters, even though the Hispanic community is larger.

For Clinton to make serious headway against Obama in the delegate counts, she needs to win Ohio and Texas by convincing margins – say, in the high 50s. If she falls short but stays in the race, analysts say, she will have to weigh potential damage to the party and to her own political future.

But there are growing signs that her core supporters – older women, union voters, low-income voters – are demanding that she hang tough, even if Tuesday's result is not convincing in her favor. All along, the conventional wisdom is that Obama supporters would be less willing to back a Clinton nomination than vice versa. But now that feeling is beginning to change among some Clinton supporters, and in Ohio – a crucial battleground in the general election – there are concerns that some Democrats would not be willing to vote for an African-American in November.

Rarely is that view expressed openly. "There's just something about Obama that makes me uncomfortable," said one woman at a Clinton event in Hanging Rock, Ohio, last week.

Almost regardless of what voters do on Tuesday, some analysts say, the best outcome for Democrats is for their nomination race to end.

"Every day that it lasts after Tuesday is a good day for John McCain," says John Zogby, an independent pollster.

Former Democratic presidential candidate Bill Richardson has not endorsed Clinton or Obama, but he tacitly threw his weight behind Obama Sunday on CBS's "Face the Nation."

"I just think the D-Day is Tuesday," said Governor Richardson of New Mexico. "We have to have a positive campaign after Tuesday. Whoever has the most delegates after Tuesday, a clear lead, should be in my judgment the nominee."