WASHINGTON -- John McCain hopes to come out with enough decisive victories in the Republican primary races on Super Tuesday to give him the edge in the presidential nominating contest, but the proportional awarding of delegates guarantees that neither he nor any other candidate will sew up the party nomination this week.

In fact, neither party is awarding enough delegates on Tuesday for anyone to clinch the nomination.

Twenty-four states hold some delegate selection event on Feb. 5, with 1,681 Democratic delegates and 1,023 Republican delegates to the national presidential nominating conventions this summer up for grabs. A candidate needs 2,025 delegates to secure the Democratic nomination, and 1,191 to win the Republican nomination.

Based on Associated Press estimations of delegates awarded in the states that already have held contests, John McCain leads with 93 delegates to his name while Hillary Clinton bests Barack Obama in her party's race with 261. Mathematically, even if both front-runners won every delegate on Super Tuesday, they can't get a majority.

This year's primary calendar "was designed to pick a candidate as quickly as possible," said Howard Wolfson, communications director for Clinton's campaign. But it didn't turn out that way, he said. Instead, "this unbelievable, grueling sprint from the 26th of December to the 5th of February ... will not result in a nominee being chosen."

That's not to say the front-runners won't go a long way toward becoming the presumptive nominee of their parties.

On the Democratic side, the sheer size of the Feb. 5 challenge could favor Clinton. She is better known than Obama and holds a lead in national polls. But with a sizable bank account and lots of attention from his win in South Carolina, Obama is prepared to go toe-to-toe with Clinton.

Tuesday's races are being played out in states both large and small, including Clinton and Obama's home states, New York and Illinois respectively. Home states for Republicans McCain (Arizona), Mitt Romney (Massachusetts) and Mike Huckabee (Arkansas) are also voting on Tuesday.

None of the Democratic contests on Tuesday awards delegates by a winner-take-all approach, which means Obama could still win a substantial share of delegates even if Clinton wins most of the states' popular votes.

"It's not going to be as decisive as we thought it would be two months ago," Obama told FOX News. "We're going to do well enough that coming out of Super Tuesday we're still going to have a competitive" race.

For Democrats, in states where an even number of delegates are being doled out, the two candidates are likely to divide the spoils no matter what. Statewide vote totals determine only 35 percent of the party's awarded delegates. The rest are awarded by congressional district, with a candidate needing at least 15 percent of the vote to get the typically three to five delegates awarded. Districts with an odd number of delegates become the most valuable because the winner will automatically get an extra delegate.

In a district with four delegates awarded, the winner must receive nearly 63 percent of the vote to get a 3-1 split in delegates, and 85 percent of the vote to win all four.

Refusing to predict the outcome, Clinton on Sunday said she is seeing huge crowds and "a lot of great activity going on on the ground" in the Super Tuesday states.

But, she acknowledged, the race is still too close to call.

"The rules in our party really are much more challenging. This whole Super Tuesday national primary is something nobody's ever gone through before. We're kind of making it up as we go. So it's hard to sit here and predict what will happen on Tuesday or what happens the next day," Clinton told "FOX News Sunday."

On the Republican side, the nine winner-take-all contests could make a big difference in propelling a candidate toward the finish line.

McCain is favored in primaries in five of them — Arizona, New York, New Jersey, Connecticut and Delaware. That's a total of 251 delegates. Losers get none, no matter how close they come.

Romney is the favorite in the primary in Utah, where a large Mormon population gives him an edge for a winner-take-all prize of 36 delegates. He also plans to attend the West Virginia convention on Tuesday in hopes of locking down all 18 delegates there.

Missouri, with 58 delegates, is a winner-take-all battleground among McCain, Romney and Huckabee.

With no shot in winner-take-all states, the candidates are free to look at other, more realistic targets. McCain will spend little time in the South; Huckabee will go virtually nowhere else. A view of polls out Sunday shows McCain with solid leads in Illinois, New York, New Jersey and Missouri, and even a six-point lead in Georgia, where Huckabee planned to concentrate his effort along with Alabama and his home state of Arkansas. Huckabee is running second but about nine to 10 points behind McCain in Missouri, and hasn't given up hope of reaching into southern conservative pockets to eke out a victory.

Romney is still working through his options, but is analyzing states where the winner of each congressional district picks up Republican delegates. He was considering making a play for some in Georgia, Alabama and California, regardless of whether he can win the entire state, one of his strategists said. One poll out Sunday had Romney ahead in California, thought it was contradicted by two others.

Part of Romney's strategy is based on the fact that California's race is a variation on the winner-take-all format, with three delegates going to the popular vote winner in each of the state's 53 congressional districts. The winner of the statewide vote picks up an additional bonus of 11 delegates.

"You know, we're going to get a test on Tuesday. We'll see how it goes. I expect to win a bunch of states and a bunch of delegates," Romney told ABC's "This Week."

Romney's home state of Massachusetts is a proportional primary. The state has 40 delegates, and an opportunistic McCain scheduled a weekend campaign stop in hopes of winning some.

McCain's emergence as the front-runner followed a victory in Florida, where he pocketed all 57 delegates and then went on to win endorsements from Rudy Giuliani, who dropped his own bid, as well as from Govs. Arnold Schwarzenegger of California and Rick Perry of Texas.

Speaking on "FOX News Sunday," McCain tried to stay humble as he edges closer to the threshold needed to win the nomination.

"Look, I haven't won this primary yet," McCain said. "I've got good people who are running. This is going to be a spirited election on Tuesday. So let's put it in the right perspective."

The Associated Press contributed to this report.