Not so in the Democratic race, where Obama and Clinton campaign seven days a week, he the strongest black presidential candidate in history, she bidding to become the first woman to sit in the White House.

Ohio and Texas vote next on March 4 — 370 convention delegates in all — and even some of Clinton's supporters concede she must win one, and possibly both, to remain competitive. Two smaller states, Vermont and Rhode Island, also have primaries that day.

With the votes counted in more than 80 percent of Wisconsin's precincts, Obama was winning 58 percent of the vote to 41 percent for Clinton.

Wisconsin offered 74 national convention delegates. There were 20 delegates at stake in Hawaii, where Obama spent much of his youth.

The Illinois senator's Wisconsin victory left him with 1,319 delegates in The Associated Press' count, compared with 1,245 for Clinton. It will take 2,025 to win the nomination at the party's national convention in Denver.

Obama's victory came after a week in which Clinton and her aides tried to knock him off stride. They criticized him in television commercials and accused him of plagiarism for using words first uttered by Massachusetts Gov. Deval Patrick, a friend. He shrugged off the advertising volley, and said that while he should have given Patrick credit, the controversy didn't amount to much.

The voters seemed not to care.

Wisconsin independents cast about one-quarter of the ballots in the race between Obama and Clinton, and roughly 15 percent of the electorate were first-time voters, the survey at polling places said. Obama has run strongly among independents in earlier primaries, and among younger voters, and cited their support as evidence that he would make a stronger general election candidate in the fall.

Obama began the evening with eight straight primary and caucus victories, a remarkable run that has propelled him past Clinton in the overall delegate race and enabled him to chip away at her advantage among elected officials within the party who will have convention votes as super delegates.

The economy and trade were key issues in the race, and seven in 10 voters said international trade has resulted in lost jobs in Wisconsin. Fewer than one in five said trade has created more jobs than it has lost.

The Democrats' focus on trade was certain to intensify, with primaries in Ohio in two weeks and in Pennsylvania on April 22.

Obama's campaign has already distributed mass mailings critical of Clinton on the issue in Ohio. "Bad trade deals like NAFTA hit Ohio harder than most states. Only Barack Obama consistently opposed NAFTA," it said.

Clinton's aides initially signaled she would virtually concede Wisconsin, and the former first lady spent less time in the state than Obama.