( Reuters ) - Barack Obama hit back at rival Hillary Clinton on Saturday before a Wisconsin showdown next Tuesday in their Democratic presidential battle, as Clinton headed to the state for the first time.
Obama, a first-term Illinois senator, has beaten Clinton in the last eight state contests to gain the upper hand in their duel to become the Democratic presidential nominee in November's election.
Obama has spent four days in Wisconsin since his last round of victories last Tuesday, while Clinton has focused on March 4 votes in Ohio and Texas hoping victories there will rejuvenate her flagging campaign.
He launched another advertisement on Saturday responding to Clinton's recent attacks. The New York senator has criticized him as more talk than action, and aired two ads in Wisconsin this week attacking his refusal to debate in the state and his health care and retirement plans.
"After 18 debates, with two more coming, Hillary says Barack Obama is ducking debates? It's the same old politics," an announcer says in Obama's new ad.
"Obama has a plan to protect Social Security benefits and the current retirement age. Hillary doesn't," the spot said.
Obama and Clinton were to appear separately on Saturday evening at a party dinner in Milwaukee. Clinton will campaign in the state on Sunday and Monday before the primary.
Democrats in Hawaii also vote on Tuesday but Obama, who was born in the state, is expected to win there.
Clinton, under pressure to slow Obama's momentum, has emphasized her economic message in an appeal to middle- and lower-income voters.
"It is time we had a president who was a fighter, a doer and a champion for the American middle class," Clinton said on Friday during an economic round-table in Cincinnati, Ohio.
"This primary election offers a very big choice to the voters of Ohio," she said. "You can choose speeches or solutions."
Clinton's criticism came as a poll showed her trailing Obama in Texas by 6 percentage points. The American Research Group survey, which had a margin of error of 4 percentage points, showed Clinton with 42 percent support versus 48 percent for Obama.
Texas and Ohio are "must win" states for Clinton, who is lagging Obama in the race for pledged delegates awarded by the state-by-state contests to pick a Democratic nominee. The delegates will choose the Democratic candidate at a nominating convention this summer.
Obama also has focused on economics in Wisconsin. On Saturday, he visited a community college to tout proposals for a tax credit to make community and technical colleges more affordable.
"We are at a moment where people are finding it harder and harder to get ahead," he said, adding his plan would "put a little wind at the backs" of average Americans.
A recent poll showed Obama with a 5-point lead in Wisconsin over Clinton.
Republican front-runner John McCain took the day off on Saturday before winning the endorsement of former President George H.W. Bush, the father of the current president, at an event in Houston on Monday.
McCain is almost certain to be the Republican presidential nominee for the November general election after defeating his main rival, former Massachusetts Gov. Mitt Romney, and winning his endorsement. McCain's nearest rival is former Arkansas Gov. Mike Huckabee, who is running a distant second.