Hillary Clinton sets foot in Wisconsin to campaign for the first time Saturday, momentarily shifting focus from her must-win March 4 contests in Ohio and Texas to make an 11th-hour challenge to Barack Obama ahead of the state's primary Tuesday.

Bill Clinton already had campaigned for her in Wisconsin two days earlier and she's still rolling out new attack ads in the state, but as the New York senator faces down the possibility of 10 consecutive losses come March 4, she's moving to blunt the damage personally before her firewall contests.

Polls show Clinton in striking distance. A Rasmussen survey from Wednesday showed Clinton trailing Obama by just 4 points, at 43 percent to his 47.

While aides say Clinton may not win Wisconsin, she wants to at least narrow the margin and keep her chin up going into Ohio and Texas, where her campaign claims it will turn the race back around. Seeking to avoid the kind of lopsided defeats she suffered in Virginia, Maryland and the District of Columbia Tuesday, she's planning to stay in Wisconsin for at least three days.

Plus she's using the state to wage attacks against Obama, which are attracting coverage elsewhere. Clinton paved her path to Wisconsin earlier in the week, with a couplet of negative ads blasting Obama for not debating her.

"Barack Obama still won't agree to debate in Wisconsin," the announcer in the latest ad says. "Maybe he doesn't want to explain why his health care plan leaves out 15 million people and Hillary's covers everyone ... Wisconsin deserves better."

Obama's taken the bait, turning the jabs into a tit for tat. He released his second ad in the volley Saturday, accusing Clinton of "the same old politics."

Obama said at a rally in Green Bay he's already had 18 debates with Clinton, with two more on the way.

"That's what happens when you've been in Washington a long time," Obama said. "Your attitude becomes, 'I'll just say whatever might work to win an election.'"

Obama backer and Wisconsin Gov. Jim Doyle has even jumped to his defense, saying in a conference call Friday that the Illinois senator already is in a "one-sided debate."

"The fact is Sen. Clinton has not even been in Wisconsin yet. She has not reached out to the voters of Wisconsin at all except through these negative campaign ads," he said. "Fact is he's out here in the state having a one-sided debate right now and the only campaign she has going on in Wisconsin is negative TV ads."

That changes Saturday, of course, when both candidates are set to attend a Democratic gala in Milwaukee.

After an internal Obama memo leaked to reporters last week projecting a 7-point victory, Clinton said Thursday she's not writing off Wisconsin.

"I hear ... Sen. Obama's campaign declared that this race was over. Well, I beg to differ," she said. "I think the people of Wisconsin and other states would like to have a say before anyone declares themselves the nominee."

Hawaii also holds caucuses Tuesday, and though the Clinton camp has sent daughter Chelsea there for three days, Obama was born in Hawaii and that alone could give him the edge.

But with 74 delegates, Wisconsin is a bigger fish for Clinton than Hawaii and its 20 delegates. The latest Associated Press tallies show Clinton with 1,220 delegates and Obama with 1,276.

As Clinton enters Obama territory, Obama's still racking up the momentum, with fresh endorsements from the Service Employees International Union and United Food and Commercial Workers union. And at least one recent poll shows him gaining in a state Clinton needs.

Delegate-rich Texas polls mostly show Clinton ahead, but an American Research Group survey Friday showed Obama with a 42- to 48-point lead over Clinton.

Plus he scored endorsements from the Houston Chronicle and Milwaukee Journal Sentinel Saturday.

Clinton still is leading in most polls in Ohio and Pennsylvania.

Vermont and Rhode Island also vote March 4, and on Friday Obama began rolling out ads in those states, focusing on his health care plan and vision for unity in Washington.

FOX News' Aaron Bruns and Bonney Kapp and The Associated Press contributed to this report.