Sen. Barack Obama won the Wisconsin Democratic primary decisively last night, extending his winning streak to nine consecutive contests and dealing another significant blow to Sen. Hillary Rodham Clinton, whose imperiled presidential candidacy now hangs on the outcome of showdowns in Ohio and Texas in two weeks.

After a week of sparring that saw the first negative ads of the campaign, Obama emerged victorious in a critical general election battleground state. For the second week in a row, the senator from Illinois made inroads into the coalition that Clinton has counted on to carry her to the nomination — women and white working-class voters — while rolling up big margins among white men.

With 97 percent of precincts reporting in Wisconsin, Obama had 58 percent of the Democratic vote and Clinton had 41 percent.

FOCUSING ON OBAMA

After winning easily in Wisconsin's Republican primary, Sen. John McCain of Arizona all but dismissed Clinton as a potential adversary, focusing his rhetorical fire on Obama as offering an "eloquent but empty call for change."

Obama celebrated his win at a boisterous Houston rally attended by an estimated 19,000 people and exhorted them to give him another important push toward the Democratic nomination in Texas' March 4 primary. "Houston, the change we seek is still months and miles away, and we need the good people of Texas to help us get there," he said. "We will need you to fight for every delegate it takes to win this nomination."

Mindful of McCain's attacks, however, he struck back at the GOP candidate. "I revere and honor John McCain's service to his country. He's a genuine hero," Obama told the audience at the Toyota Center. "But when he embraces George Bush's failed economic policies, when he says he's willing to send our troops into another 100 years in Iraq, then he represents the party of yesterday, and we want to be the party of tomorrow."

Clinton was in Ohio, the other big March 4 state, appearing at a rally in Youngstown, where she did not acknowledge the Wisconsin results and another setback that pushed her further from the nomination that at one time seemed hers almost for the asking. Instead she focused on the road ahead and the choices she said now confront Democratic voters.

She said: "One of us is ready to be commander in chief in a dangerous world. ... One of us has a plan to provide healthcare for every single American — no one left out. ... One of us has faced serious Republican opposition in the past. And one of us is ready to do it again."

Clinton aides said she called Obama to congratulate him after the outcome became clear.

If the Wisconsin campaign was any indication, the next two weeks could be the most negative of the Democratic race. The Clinton team has seized on a series of issues and Obama statements to challenge his readiness to be president and his credibility as a candidate. Obama has not shied from firing back, using his stump speeches to issue pointed rebuttals of Clinton's criticism and airing response ads to her television commercials, while his advisers have sparred with Clinton's in a flurry of daily conference calls and press releases.

READY TO DEBATE

An opening test for the candidates will come tomorrow night in Austin, when the candidates meet in their first debate since before the Feb. 5 Super Tuesday contests. Clinton's campaign sees that debate, and a second one next Tuesday in Cleveland, as her best opportunity to shift voters away from talk of Obama's growing momentum.

There were 74 convention delegates at stake in Wisconsin last night, along with 20 in Hawai'i.

Even before Wisconsin and Hawai'i, Obama held a lead over the senator from New York in delegates awarded in the primaries and caucuses. When so-called superdelegates — the 795 Congress members, governors and other party officials with automatic credentials for the Democratic National Convention — are included, he is still ahead, but by a narrower margin.

About 30 percent of pledged delegates have yet to be awarded and several hundred superdelegates remain uncommitted. But, given Democratic rules that award delegates proportionally, Obama's slowly expanding margin will become more difficult for Clinton to overcome unless she can win upcoming contests by huge margins.