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.