The presidential prospects of Bill Bradley and John S. McCain hang in the balance today, as voters cast their ballots in the delegate-rich Super Tuesday primary and caucus contests.

Beginning this morning, Democrats, Republicans and independents will vote in 15 Democratic and 13 Republican contests, choosing which candidate will benefit from more than half the delegates needed to win the two party's nominations.

In Massachusetts, where state officials predict a high turnout, McCain and Vice President Al Gore '69 have commanding leads in the latest polls.

McCain trails Texas Gov. George W. Bush in many of the larger states--but Gore leads Bradley in almost every voting district across the country.

And a senior Bradley aide conceded that a poor performance today would likely spell the end of the former New Jersey senator's candidacy.

Thomas Patterson, Bradlee professor of press and politics at the Kennedy School of Government, said Bradley peaked in November and December due to voter backlash against Gore and the "easygoing" nature of the early part of the campaign.

"He had plateaued by early January," Patterson said.

As Gore began to pick apart Bradley's proposed health care proposal, saying that senior citizens and minorities would be disadvantaged by it, Bradley began to lose momentum, particularly among core Democratic constituencies, Patterson said.

Gore's widespread support among the national Democratic Party apparatus and the vice president's union endorsements have not made Bradley's task any easier.

Still, Ed Turlington, Bradley's deputy campaign manager, said he thinks his candidate has a shot at winning the Massachusetts primary.

Turlington said Bradley has a strong organization in the state and that the campaign has spent a lot of money, particularly on Boston-area television ads.

"If Bill can win in places like Massachusetts, it will help the race keep going," he said.

Turlington said Bradley's showing in Washington's primary last week was "disappointing", but added that today's primaries--"a snapshot of America"--will show whether Bradley's message has gotten across.

"We did it, it's over, so now we point to March 7," he said.

On the Republican side, Patterson predicted that McCain will benefit from the support of independents, as he did in New Hampshire and Michigan.

Patterson said that 25,000 Massachusetts voters changed their party affiliation from Democrat to independent or Republican before the primary.

"John McCain would get the large percentage of those voters," Patterson said.

He said that since many voters subscribe to the consensus view that Gore has wrapped up the Democratic nomination, more voters will participate in the still-viable Republican race.

"There is still a little bit of life left in the Republican race," he said.

Titanic Tuesday

Outside Massachusetts, crucial battles will take place in the delegate-rich states of California, New York and Ohio.

Except for Connecticut, where McCain and Bush are in a dogfight, the former senator from Arizona is expected to sweep the New England states--but Bush will most likely win the delegates in California, Georgia, Maryland, Missouri and Ohio.

The blanket primary in California, where voters are presented with a ballot that includes candidates from all parties will likely be the most intriguing to watch.

McCain might receive more votes overall, but Bush will probably win all of the state's 162 delegates. Whatever independent and Democratic support McCain receives, only Republican voters' ballots will count in the race for the GOP's delegates.

"Bush is going to win big-time for the delegates," said Henry E. Brady, a professor of political science and public policy at the University of California at Berkeley.

But if McCain wins California's popular vote or "beauty contest," the New England states and New York, his campaign would still be alive, Brady said.

"It'd be hard to say he's out of the race," he said.

In both New York and Connecticut, the two Republican contenders are neck-and-neck, according to Maurice Carroll, director of the Quinnipiac College Polling Institute in New York.

In a poll he released yesterday, Bush held a nine percentage point lead, though McCain held a seven percent advantage lead over the Texas governor March 1.

Carroll said the late Feb. speech McCain gave in Virginia criticizing Pat Robertson and Jerry Falwell appears to have hurt him, even though it was designed to attract voters in California and New York.

"That speech appears to have [had] a boomerang effect, which is peculiar, but hey--it's a peculiar year," Carroll said, adding that California's primary system, approved in 1996, is "nutty".

McCain's chances in New York will depend on his ability to win without independent voters, Carroll said.

"He's been on a high-wire act ever since this thing started," he said. "It's still a high-wire act for McCain."

But for Bradley, the high-wire act appears to have reached its end. He trails Gore in all Democratic primaries taking place today, including California and New York.

Turlington said "very few people" would have given Bradley's campaign a chance one-and-a-half years ago.

"Against that establishment power, we've accomplished a lot," he said. "All over the country, students have gotten involved."

Rachel E. Taylor '03, a Bradley supporter, said Bradley is the only candidate willing to talk about race and to change education. She said she cannot understand why more progressive voters have not cast their ballots for Bradley.

"I'm kind of at a loss to figure out what's going on in the country...[and] what people are thinking," Taylor said.