WASHINGTON — Super Tuesday may be tantamount to a national primary, but at least for Democrats, it won’t crown a winner.

While voters in the 22 states that head to the polls tomorrow represent more than half the country, no matter what happens, the campaigns of senators Clinton and Obama will be alive and kicking on Wednesday morning. Even when added to delegate tallies from the early states, the 1,681 delegates at stake will not allow either contender to clinch the Democratic nomination, which requires 2,025 delegates.

Because delegates in the Democratic Party are awarded proportionally, the two-person race may be as tight coming out of Super Tuesday as it is heading in.

Analysts say that with polls showing a razor-thin margin separating Mrs. Clinton and Mr. Obama in many large states, the chances for either candidate to deliver a knockout blow tomorrow are unlikely. “I just don’t see any scenario whereby either of them is going to pull out,” a former Democratic consultant who serves as interim dean of Boston University’s College of Communication, Tobe Berkovitz, said.

The campaigns are also looking ahead. Although Mr. Obama has trailed Mrs. Clinton nationally and in delegate-rich February 5 states such as New York, New Jersey, and California, he has already purchased television ads in six states that vote over the next week, including Washington State, Louisiana, and Nebraska, which go to the polls February 9, as well as Maryland and Virginia, which hold primaries February 12.

On the Republican side, the path has more clarity. Senator McCain cannot mathematically secure the 1,191 delegates he needs to capture the Republican nomination tomorrow, but given his widening lead in national polls and likely victories in large, “winner-take-all” states, he can come awfully close. Carrying momentum from a win in Florida last week and the endorsements of Mayor Giuliani and Governor Schwarzenegger, Mr. McCain appears to be distancing himself from his nearest rival, Mitt Romney.

National polls show the Arizona senator with a lead of nearly 20 points, and unlike under the proportional rules for Democrats, Mr. McCain can gobble up dozens of delegates at a time with narrow victories in a few key states. He is ahead in New York, New Jersey, Connecticut, Missouri, and Arizona — each winner-take-all primaries that together carry nearly 300 delegates, or 30% of the 975 at stake for Republicans tomorrow.

Mr. Romney is banking on wins in his home state of Massachusetts and Utah, site of a significant Mormon population, but without a stronger-than-expected showing elsewhere, he may wake up Wednesday morning to see Mr. McCain with a near insurmountable lead in delegates and momentum. The former Massachusetts governor is also hurt by the presence of Michael Huckabee, who could prevent him from picking up crucial delegates in the South, where the Republican base is dominated by social conservatives.

For Mrs. Clinton and Mr. Obama, there are relatively few opportunities to run up the delegate score. Their best bets are likely in their home states: New York and Illinois. Mrs. Clinton’s lead in the Enpire State is nearly 20 points, according to the Real Clear Politics average, while a Chicago Tribune/WGN poll yesterday showed Mr. Obama ahead by 31 points in Illinois. Because any candidate who reaches a 15% threshold in a voting district earns delegates, neither candidate is likely to sweep their home state.

Mr. Obama in particular is trying to pick off delegates in New York. “The campaign has targeted 5 NYC congressional districts where they think we can steal a lot of delegates from Hillary,” an e-mail message obtained by The New York Sun that was sent to potential contributors late last week by a top local fund-raiser for Mr. Obama, Gordon Davis, reads. The e-mail message appeals for immediate donations from supporters who had not already contributed the maximum $2,300 to Mr. Obama’s campaign. Mr. Davis listed the targeted congressional districts as the seats held by Reps. Charles Rangel, Carolyn Maloney, Jerrold Nadler, Edolphus Towns, and Yvette Clarke.

Mrs. Clinton appears to be leading in several other “Super Tuesday” states, including Massachusetts, New Jersey, and Tennessee. Mr. Obama is ahead in Georgia, but the race is too close to call in the largest state, California, and in several others, including Missouri, Alabama, and Connecticut.

One possible outcome from tomorrow’s primaries is a battle for spin and momentum in which one candidate winds up with narrow victories in a majority of states, but only a negligible lead in delegates because of the proporational allocation rules. “You get bragging rights that you won in all these big states — and I’d much rather be that person — but the other one can say, ‘Well, look at the delegate count,'” Mr. Berkovitz said. “You can call this Super Duper Muddle Tuesday.”

In that scenario, the campaigns would likely gear up not only for the eight other states and the District of Columbia that hold primaries and caucuses in February, but for the next “Super Tuesday,” March 4, when nearly 400 delegates will be up for grabs in Texas and Ohio.