Kerry, the four-term Massachusetts senator, solidified his front-runner status with a win in Delaware and projected wins in Missouri and Arizona.
Edwards, a one-term North Carolina senator, countered with a solid win over Kerry in South Carolina, a victory that keeps his campaign alive and sets him up as Kerry's number one challenger.
The evening's closest race was in Oklahoma where Edwards and retired Gen. Wesley Clark were locked in a neck-and-neck race, with Kerry a few points back.
Howard Dean was shut out along with Joe Lieberman, who dropped out of the race without a win in a single state.
"It's a huge night," Kerry said. "I'm stunned by it.
Aiming for victories in several other states, Kerry dismissed Edwards' singular win.
"I compliment John Edwards, but I think you have to run a national campaign, and I think that's what we've shown tonight,'' Kerry said. "You can't cherry-pick the presidency."
Missouri and Arizona were the night's biggest prizes, with 129 delegates at stake – nearly half of the 269 delegates up for grabs Tuesday. In state after state, Kerry won among voters who wanted a candidate with experience or who could beat President Bush, exit polls showed.
Edwards had said he must win South Carolina – and he did. With 1,597 of 2,008 precincts reporting in South Carolina, Edwards had 45 percent of the vote to 30 percent for Kerry. Clark and the Rev. Al Sharpton were well back in a fight for third place.
"I think tonight I proved that I can win the White House and change the country in a way that strengthens the millions of middle-class families that Bush has forgotten, and lift up the 35 million Americans who live in poverty," Edwards said.
New Mexico and North Dakota were also holding contests on the biggest night so far in the 2004 race for the White House.
CBS News exit polls showed Democratic primary voters in five states were leaving the polls with one thing on their minds – the economy. Around one-third of voters in Missouri, Oklahoma, Delaware and Arizona rated the current state of the economy and the job situation the top issue in the election. In South Carolina, 46 percent rated it the top issue.
Three-quarters or more of voters in each state dub the economy "not good" or "poor" and many have felt the effects in their own pocketbooks, saying they are financially worse off today than they were four years ago.
Edwards appealed to South Carolinians as an empathetic candidate, who cares about their concerns, according to CBS News exit polls. His base of support was made up of typical Southern Democrats – moderate and conservative voters, as well as whites.
Edwards performed well among voters who called themselves political independents (nearly one quarter of the primary electorate) – winning just over half of their votes. In addition, he won nearly half of voters who labeled themselves as ideologically moderate or conservative.
Black voters, who made up nearly half of the electorate, split their votes between Edwards and Kerry. The Rev. Al Sharpton received only one in five African-American votes.
The CBS News exit polls were conducted for the National Election Pool by Edison / Mitofsky among 1,554 voters in Arizona, 777 in Delaware, 891 in Missouri, 955 in Oklahoma, and 1,284 in South Carolina. The margin of sampling error for Arizona, Oklahoma and South Carolina is + 4 percentage points, and + 5 percentage points for the remaining states.
For both Clark and Edwards, victory in one state may not be enough. While targeting South Carolina, Edwards hoped to upset Kerry in Oklahoma or elsewhere to emerge as the front-runner's chief rival. Democrats award delegates based on a candidates' showing in congressional districts, giving Kerry's rivals a chance to grab a few delegates even in states they lose.
Dean, the former Vermont governor, ran out of cash and momentum after finishing third in Iowa and a distant second in New Hampshire. He ran no TV ads in the seven states and intended to stay off the air for a spate of other contests until Feb. 17, when Wisconsin votes.
On a deeply divided staff, some Dean aides were focused on raising money to cover campaign debts, an emphasis that gave a backseat to costly political tactics such as television commercials.
Lieberman announced he was ending his presidential bid after failing to rack up a single state win.
"Am I disappointed? Naturally. But am I proud of what we stood for in this campaign? You bet I am,'' he told supporters in Arlington, Va.
The race turns next to Michigan and Washington state, with a combined delegate total of 204. Maine, Tennessee, Virginia, the District of Columbia, Nevada, Wisconsin, Hawaii, Idaho and Utah hold primaries or caucuses before a mega-state showdown March 2.
That's when delegate-rich California, Georgia, New York and Ohio join six other states for primaries or caucuses. Party leaders expect the nomination to be wrapped up by March 9, when Florida, Louisiana, Mississippi and Texas vote.
The last elections are June 8 in New Jersey and Montana, but Democrats hope to have a presumptive nominee in place well before then.
Al Gore wrapped up the Democratic nomination in 2000 in early March, defeating Bill Bradley on a multistate election night. In that race, several weeks separated the New Hampshire primary, won by Gore, and the decisive contest in March.
Democratic leaders moved up several contests this primary season, hoping to unite the party behind a candidate early to challenge Bush, whose has raised at least $140 million.