They didn't call Bill Clinton the "comeback kid" for nothing. But if his wife, New York Senator Hillary Clinton, wants to continue the family tradition of rising from the dead in presidential races, March 4 is the day. Although she steamed her way through 2007, acting and talking like the front-runner she was, in Tuesday's primaries, the final major contests of the season, Clinton is teetering on the razor's edge between a historic revival and an unprecedented collapse.

Trailing fellow Democratic Senator Barack Obama in delegates (1,370 to 1,274, according to The Associated Press) and states won (24 to 11, not counting Florida and Michigan, whose results, so far, aren't being recognized), and coming off an 0-11 streak since Super Tuesday, Clinton's camp has openly called Tuesday's contests her "firewall."

While neither Democrat will be able to sew up the nomination on Tuesday, Republican front-runner and presumptive nominee Senator John McCain could finally claim his party's top prize with big wins. With 1,013 delegates in hand, McCain is fewer than 180 delegates from the 1,191 needed to secure the nomination, with his only competition, former Arkansas Governor Mike Huckabee, barely visible in the rearview mirror with 257 delegates.

Clinton has been counting on March 4 wins to keep her campaign afloat, but Obama's momentum has grown exponentially since the last big delegate scramble. At press time, Clinton still held a razor-thin lead in one of the two big-prize states: Ohio (141 delegates), where she had a double-digit lead just weeks ago. Obama had also closed the once-formidable gap in Texas (193) and, according to a Reuters report, actually pulled slightly ahead of Clinton in the Lone Star State just days before the contest.

No less an authority than former President Clinton himself said that Tuesday is make-or-break time for the ex-first lady. "This whole nominating process has come down to Texas and Ohio," he said last week. Even if Clinton doesn't win either state by convincing margins, or loses both in close races, she would still be close enough to likely stay in the race through spring, considering neither candidate is expected to reach the magic number of 2,025 delegates before the August convention in Denver.

Neither Democratic candidate has spent much time in the other two states up for grabs Tuesday: Rhode Island (32), where Clinton has strong ties, and Vermont (15), which neither has visited, but where Obama is reported to have a commanding lead over Clinton.

The job for McCain is a bit easier, as his hard work on immigration reform has won him a lot of support in Texas' (137) Hispanic community, which could make up nearly 40 percent of the total voting public. At press time, he held comfortable double-digit leads in Texas, as well as Ohio (85), where a Zogby poll put his lead at 62 percent to Huckabee's 19 percent. McCain was also holding onto leads in Vermont and Rhode Island, which each offer 17 delegates.