(CBS) This analysis was written by CBSNews.com senior political editor Vaughn Ververs.
Hillary Clinton did something last night she had not been able to do since New Hampshire - stop Barack Obama's momentum in the Democratic primary contest. Or at least blunt it.
By winning three out of the four primary contests Tuesday night, Clinton almost certainly saved her campaign to fight on in a contest that now looks likely to stretch at least another seven weeks - until Pennsylvania votes.
Clinton can now boast of two more wins in big states, having carried Ohio and Texas (as well as Rhode Island), but she did nothing to erase Obama's sizeable delegate lead. In fact, she may have lost ground by the time all the delegates are awarded.
It's hard to see a path to the 2,025 delegate threshold needed to win the nomination for either candidate without the support of a sizable number of super delegates. So, the argument will rage on, muddied enormously by last night's results.
Despite the fact that Clinton once held enormous leads in Texas and Ohio, Obama came roaring into the evening on the precipice of ending the contest. The winner of 12 straight contests, he repeated his pattern of erasing those big leads. But, unlike big wins in Virginia, Maryland and Wisconsin, Obama couldn't get over the top and seal the deal.
"We're going on, we're going strong and we're going all the way," Clinton said in Ohio Tuesday night. "We're just getting started." Coming into the night, the New York Senator was expected to face increased pressure from party leaders and insiders to exit the race if she failed to win the two big states at stake. Now that she has - and added Rhode Island to boot - where such pressure would come from is less clear.
Obama's campaign argues that this is less a race about winning states and more about winning delegates. But winning pledged delegates alone probably won't get him the nomination, as long as Clinton remains in the race, splitting the haul to the end.
The recent sharpening of the argument Clinton has pressed, along with outside events, may have helped her stem the tide. Her campaign in Texas launched a much-discussed ad raising questions about Obama's readiness to handle a crisis as president. Obama's campaign got caught up in a series of revised statements about what one of his economic advisers said to a Canadian official about NAFTA. Meanwhile, the trial of Chicago developer Tony Rezko, a former Obama supporter, thrust that issue back into the headlines.
Whether any of these developments mattered to voters in Texas and Ohio is unclear, but they marked the first time Obama had entered such an important contest while facing tough questions. Having won a variety of states with large margins since Super Tuesday, it's fair to say Democrats last night may have cumulatively expressed some buyer's hesitation.
What comes next is uncertain. Wyoming holds caucuses on Saturday and Mississippi's primary is next Tuesday. Both should be strong states for Obama but aren't likely to be enough to knock Clinton out, should she lose them.
Then it is six long weeks before the next contest in Pennsylvania. To put that in perspective, the Iowa caucuses were held just nine weeks ago. Those are six weeks that presumptive Republican nominee John McCain will have to ready his general election campaign, six weeks in which Clinton may yet face more pressure to bow out and six more weeks for Obama to weather the kinds of issues he's faced in the past several days.
A prolonged race also raises an issue most Democratic leaders would rather avoid - what to do with Michigan and Florida. Both states, stripped of all their delegates by the national party for moving their primaries earlier than February 5th, were won by Clinton, and they are not insignificant states.
Obama's campaign is unlikely to allow those delegates to be restored and allocated on the basis of those earlier results as long as they have a breath left. Ditto for Clinton; unlikely to ever agree to splitting them evenly or in proportion to current totals. We could yet end up with two more major primaries at the end of this crazy process.
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