OSHKOSH, Wis. &

Reflecting on his recent string of victories in the battle for the Democratic presidential nomination, Sen. Barack Obama was jabbed Friday by his political rivals in both major parties and in a new television ad playing in Wisconsin.




The presumptive Republican nominee, John McCain, tried to put the Illinois senator on the spot about whether he would accept public financing for the November election &

an act that would drastically curtail campaign spending.




McCain, an advocate of political finance reform whose campaign nearly went broke last summer, told reporters here that he believed Obama last year had said he would accept public financing.




"It was very clear to me that Sen. Obama had agreed to having public financing of the general election campaign if I did the same thing," McCain said. "I expect Sen. Obama to keep his word to the American people."




McCain suggested his campaign would accept public funds &

which would limit his spending to about $85 million from the Republican convention in early September through election day &

only if the Democratic nominee does. He recently sent letters to the Federal Election Commission and the Treasury Department opting out of the public funding for the primaries.




McCain senior adviser Mark Salter sidestepped speculation that the Arizona senator might be mainly concerned with Obama's fundraising prowess.




"The campaign is concerned that the self-proclaimed tribune of the 'new politics' doesn't start off the general election campaign by breaking his word to the American people," Salter said.




Obama, speaking to reporters earlier in Milwaukee, dismissed the debate over financing as premature.




"If I am the nominee I will make sure our people talk to John McCain's people to find out if we are willing to abide by the same rules and regulations," Obama said. "It would be presumptuous of me to start saying now that I am locking in to something when I don't even know if the other side will agree to it. And I'm not the nominee yet."




On another front, the campaign of rival Democrat Hillary Rodham Clinton released an ad, called "Deserved," in which the New York senator criticizes Obama again for not agreeing to a Wisconsin debate before Tuesday's primary.




The ad also accused Obama of voting for "billions in Bush giveaways to the oil companies" contained in the 2006 energy bill that Clinton opposed, and it said he "might raise the retirement age and cut benefits for Social Security." That charge referred to televised comments Obama made in May that "everything should be on the table" in trying to resolve projected long-range shortfalls in the massive entitlement program.




Wisconsin Gov. James E. Doyle, who has endorsed Obama, shot back by chastising Clinton for spending the week stumping in Ohio, which votes March 4, instead of Wisconsin. Clinton is scheduled to be in Wisconsin beginning Saturday.




"To have Sen. Clinton launch these false and negative ads and somehow criticize him for not being straight with people in Wisconsin is more of these politics he's trying to do away with," Doyle said. "To claim he's a lackey for the big oil companies is just laughable. ... This is the kind of politics that up to this point in the campaigns before Wisconsin, the candidates had avoided."




Clinton spent the day in Ohio, focusing on economic issues and continuing her efforts to paint Obama as a candidate of rhetoric, not change.




Speaking at a Cincinnati diner with chili-dog-slinging line cooks nearby, Clinton told voters at an "economic roundtable" that reversing the nation's economic troubles would take more than talk.




"You can choose speeches or solutions," Clinton said. "You can choose thoughts or actions."




Clinton called for capping credit card rates at 30 percent and instituting a 90-day moratorium on home foreclosures to relieve the nation's financial stress. She also repeated her pledge to push for universal health care.




another issue that she portrays as offering a sharp contrast between the two candidates.




Obama, in Milwaukee, dealt with questions over gun control a day after the killings, in his home state, on the campus of Northern Illinois University.




Obama repeated his support for the constitutional right to bear arms but said the nation must do "whatever it takes" to end gun violence through background checks and other regulations that he said would not curtail Second Amendment rights.




Obama received a boost from an endorsement by the 1.9 million-member Service Employees International Union, whose organizing skills could augment the grass-roots focus of his campaign.




McCain also might be on the verge of announcing a major endorsement. He acknowledged that he would travel to Houston for a Monday news conference with former President George H.W. Bush, although he stopped short of confirming it would be for an endorsement.




Reston reported from Oshkosh, Wis., Riccardi from Cincinnati and Akron, Ohio. Staff writers Maria L. La Ganga in San Francisco and Scott Martelle in Los Angeles contributed to this report.