DETROIT (AP) — Hillary Rodham Clinton won Michigan's Democratic primary in a race that left many Democrats frustrated because she was the only major candidate on the ballot.

None of the Democratic candidates except Dennis Kucinich campaigned here, and Barack Obama and John Edwards went so far as to pull their names from the ballot to avoid angering Iowa and New Hampshire, which didn't like other states crowding to the front of the election calendar.

Some political observers said the pair dropped out to avoid a certain loss to Clinton, who has consistently led in polls. Edwards had hoped Democrats would hold caucuses, where he might have done better because of his support among union members who traditionally play a large role in such races.

Instead, Michigan went ahead with joint Republican and Democratic primaries. The contest brought the state a flood of attention from GOP candidates, but left Democratic voters unhappy with a ballot that gave them a choice of only Clinton, Kucinich, Mike Gravel, Uncommitted and Chris Dodd, who had dropped out of the race.

Lawmakers briefly toyed with legislation that would have forced the missing candidates to put their names on the ballot. When that failed, supporters of Obama and Edwards urged voters to back uncommitted in the hopes of winning some national convention delegates for their favorites.

Their strategy paid off. With 100 percent of the vote counted, nearly 40 percent of voters — 236,723 — had chosen uncommitted.

Clinton got about 55 percent of the vote, clinching a victory in a state that could prove crucial to her hopes of winning the White House in November. Kucinich got nearly 4 percent of the vote and Gravel and Dodd each got less than 1 percent.

Exit polling showed that 35 percent said they would have voted for Obama if he'd been on the ballot; of those, 79 percent chose to vote for uncommitted. Of the 12 percent who would have backed Edwards, 57 percent voted for uncommitted. Sixty-eight percent of black voters said they backed uncommitted, while 63 percent of white voters said they backed Clinton. Among female voters, exit polling showed Clinton got 60 percent of the vote, while uncommitted got 36 percent.

Former Michigan Gov. James Blanchard, a co-chairman of Clinton's Michigan campaign, said he was thrilled the New York senator won.

"The national media did not really give much credence to the Democratic primary here," which was what Obama and Edwards wanted, he said. But "it was good that she kept her name on the ballot. ... I see it as a wonderful springboard to November."

Michigan has been stripped of its 156 national convention delegates for breaking party rules by moving up its convention, but party leaders expect the delegates will be seated at the convention.

Blanchard said Tuesday's victory means most of those delegates will be Clinton supporters.

"It's a major boost in delegates, and certainly a major boost here for Hillary," he said.

Michigan Democratic Party Chairman Mark Brewer, however, said the large vote for uncommitted means a lot of delegates who support other Democratic candidates also will be in the Michigan delegation.

He said he has warned the candidates that the eventual nominee will need to campaign extensively in Michigan before the general election to make up for not campaigning before the primary.

"There's short-term disappointment about the way the primary worked out. But we're tremendously excited about winning in the fall," Brewer said. "There's tremendous energy out there."

Exit polling showed 56 percent of voters who said they were a union member or had a union member in the household backed Clinton, while 40 percent backed uncommitted. She also got 60 percent of the vote among those who describe themselves as Democrats and 37 percent of independents. But 51 percent of those who consider themselves independents voted for uncommitted.

The results are from exit polls Tuesday in 40 precincts around Michigan for the AP and television networks by Edison Media Research and Mitofsky International. The Democratic poll interviewed 997 voters and the sampling error was 5 percentage points.