WASHINGTON — They've had their say, the people of Iowa, New Hampshire, South Carolina and Florida. Now, tens of millions of Americans across the country will get to weigh in Tuesday on who should lead the two major parties into the fall presidential election.
Tuesday's unprecedented flood of caucuses and primaries will give voice to as many as 80 million voters in 24 states, a diverse chorus that could anoint one party's nominee, break the stalemate in the other party and test both parties' coalitions.
What these voters say could effectively decide the Republican presidential nomination, if they jump on board John McCain's bandwagon or rally behind challenger Mitt Romney as the anti-McCain. Polls suggest that they're leaning toward McCain.
They also could break the running tie between Democrats Hillary Clinton and Barack Obama and give one a real burst of momentum — or deliver another split decision that sends them on to grapple state by state, delegate by delegate, into the spring.
The Super Tuesday contests, however, threaten to deepen divisions in both parties, racial and generational for the Democrats and conservative vs. moderate for the Republicans. That challenges candidates in both parties who want to turn out their base of support but still hope to really the other side behind them for the fall campaign.
The test is greater, perhaps, for Arizona Sen. McCain, who emerged as the Republican front-runner with a win Tuesday in Florida.
According to polls, he leads in such big delegate-rich states as Arizona, California, Connecticut, New Jersey and New York, many of them winner-take-all contests. He could easily win the majority of the 1,009 delegates available Tuesday.
He can't lock up the title Tuesday, though. Even if he won every delegate in the 21 states with Republican contests, he'd be 89 short of the 1,191 needed to win the nomination at the Republican National Convention this summer in St. Paul, Minn.
But taking a solid majority would give him undeniable momentum, draw a new infusion of campaign cash from donors and probably draw more fence-sitting Republican officials into his camp.
"It looks like he's on his way to being the nominee," said Scott Reed, a veteran Republican strategist who ran former Kansas Sen. Bob Dole's 1996 presidential campaign.
It also would create pressure on former Massachusetts Gov. Romney to show his donors — or his family, whose inheritance he'd be spending if he lent his campaign more money — how and where he could overtake McCain. After Tuesday, another 1,133 delegates will remain to be won — enough to grasp the nomination — but he'd have to take the vast majority of them.
A key question for Republicans is whether McCain will pull the party apart — supported by moderates but driving away conservatives. That chasm is growing wider by the day now that McCain appears the favorite.
He's won so far with the lopsided support of moderates, liberals and independents, and he stands to gain Tuesday in states such as California and New York with large numbers of moderate Republicans.
But conservatives haven't rallied to him, and influential conservatives such as radio talk-show host Rush Limbaugh bitterly oppose him because of his votes against the Bush tax cuts, his outspoken criticism of torture as an interrogation technique for suspected terrorists and his advocacy — since suspended — of a path to citizenship for illegal immigrants who already are in the United States.
"It's personal," Republican pollster Whit Ayres said.
"John McCain is OK on most of the issues that conservative voters care about. But he's stuck his fingers in the eyes of conservatives on a number of issues and makes his arguments in ways that sound like he's accusing the other side of corruption."
It's personal on the Democratic side as well, but in different ways.
New York Sen. Clinton and Illinois Sen. Obama are basically the same on big issues: Both propose to expand health care to the uninsured, say they'd raise taxes on the wealthy and say they'd withdraw troops from Iraq.
They differ slightly, however, in how they say they'd reach those goals, and in whom they're appealing to.
Clinton stresses her experience in government, saying she knows how to pull the levers of power and push an agenda through Congress. Obama runs as a visionary who'd transform politics by inspiring a broad new coalition united behind change.
In the process, they've played hardball politics that's attracting different coalitions. Hers is older women, downscale whites and Latinos. His is young people, affluent whites and blacks.
They face one another Tuesday across a diverse political landscape in all corners of the country, when 1,681 delegates are up for grabs in 22 states. It will take 2,025 to secure the nomination.
African-Americans are at least 15 percent of the population in four Southern States and three others: Alabama, Arkansas, Delaware, Georgia, Illinois, New York and Tennessee.
Hispanics are at least 15 percent of the population in five states, four of them in the West: Arizona, California, Colorado, New Mexico and New York.
If Clinton and Obama opened a racial divide in recent weeks — the South Carolina vote in particular was divided clearly along black-white lines — the two worked this week to heal the rift with a polite debate in California.
At least one Democratic strategist was optimistic that their feud didn't open a permanent racial divide.
"It scratched at the scab, but I'm not sure it peeled it off," Democratic pollster Mark Mellman said. "And it's not damaging for the long term."