Waukesha, Wis. ? Republican presidential candidate John McCain said Thursday that questions about Democratic rival Barack Obama’s association with a former war protester linked to Vietnam-era bombings are part of a broader issue of honesty.

In his strongest personal criticism since his faltering campaign began casting Obama as an unknown and unacceptable candidate, McCain told supporters that Obama had not been truthful in describing his relationship with former radical William Ayers. The Arizona senator also said Obama himself has “a clear radical, far-left pro-abortion record.”

McCain and the Republican National Committee also launched new Web and TV ads about Obama and Ayers.

Loud cheers from 4,000 people gathered at a sports complex near Milwaukee greeted McCain’s attacks over Ayers, who helped found the Weather Underground, a Vietnam protest group that bombed government buildings 40 years ago. Obama has noted that he was a child at the time and first met Ayers and his wife, ex-radical Bernadine Dohrn, a quarter-century later.

“Look, we don’t care about an old, washed-up terrorist and his wife,” McCain said. “That’s not the point here.”

“He’s a terrorist!” a man in the audience screamed without making clear to whom he was referring.

“We need to know the full extent of the relationship,” McCain replied. Later, McCain told ABC News: “It’s a factor about Sen. Obama’s candor and truthfulness with the American people.”

Obama has denounced Ayers and his violent actions and views. He dismisses McCain’s criticism as an effort to “score cheap political points.”

The Associated Press and other news organizations have reported that Obama and Ayers, now a college professor who lives in Obama’s Chicago neighborhood, are not close but that they worked together on two nonprofit organizations from the mid-1990s to 2002. In addition, Ayers hosted a small meet-the-candidate event for Obama in 1995 as he first ran for the state Senate.

Meanwhile in Ohio, Obama told Ohio voters Thursday that McCain’s mortgage buyout plan would cost them billions of dollars and reward bad behavior by lenders.

Speaking in Dayton as he started a two-day bus tour of hotly contested Ohio, Obama said McCain’s plan would force the government to absorb the full cost of renegotiating mortgages to keep borrowers from losing their homes. He said lenders should share some of the costs.

The Democratic presidential candidate’s campaign also criticized McCain’s mortgage plan in a new 30-second ad to air nationally on cable TV, a relatively inexpensive way of drawing media attention to an issue.

Both candidates are competing hard for Ohio’s 20 electoral votes, which were pivotal in President Bush’s victory four years ago. Obama campaigned in Dayton, Cincinnati, Georgetown and Portsmouth on Thursday, with two more Ohio stops planned today. He will return next week to Toledo to prepare for Wednesday’s debate on Long Island, N.Y.

Obama took another jab at McCain, whose family owns several houses, when he renewed his call to change bankruptcy laws to help hard-pressed borrowers keep their homes.

“Right now, the law lets bankruptcy judges write down your mortgage if you own six or seven homes,” he said, “but not if you have only one.”

“That might help Sen. McCain sleep easier at night, but it won’t do anything for folks like you,” Obama told thousands at a baseball stadium.

Obama said McCain’s mortgage plan “punishes taxpayers, rewards banks and won’t solve our housing crisis.”