The warnings of massive retaliation came as McCain's running mate, Alaska Gov. Sarah Palin, took on the role of attacker and said that Obama sees America as so imperfect "that he's palling around with terrorists who would target their own country." She was referring to an early Obama supporter, 1960s radical Bill Ayers, a founder of the Weather Underground whose members were blamed for several bombings when Obama was a child.
Obama has denounced Ayer's radical views and activities. But he's not above questioning McCain's character with loaded words. On Sunday Obama unveiled a TV ad on the economy that paints McCain was "erratic in a crisis." Some see that as a reminder of McCain's age, 72.
Democrats were well-synchronized Sunday, using the word "erratic" and Keating's name in nearly-matching sentences across the talk show circuit.
"This is going to be a month, I think, of character assassination," Sen. Dianne Feinstein, D-Calif., an Obama supporter, said on CBS's "Face the Nation."
Indeed, McCain adviser Greg Strimple predicted "a very aggressive last 30 days" of the campaign.
"We are looking forward to turning a page on this financial crisis and getting back to discussing Mr. Obama's aggressively liberal record and how he will be too risky for Americans," he said in a recent conference call with reporters.
Obama, too, alluded to harsher tactics in a speech Sunday to thousands of people in Asheville, N.C.
McCain and his aides, Obama said, "are gambling that he can distract you with smears rather than talk to you about substance. They'd rather try to tear our campaign down than lift this country up. It's what you do when you're out of touch, out of ideas, and running out of time."
Noting the nation's serious economic problems, Obama said: "Yet instead of addressing these crises, Senator McCain's campaign has announced that they plan to turn the page on the discussion about our economy and spend the final weeks of this campaign launching Swiftboat-style attacks on me."
Obama has denounced Ayers' radical views and activities. However, Ayers hosted a small gathering for Obama in 1995, early in his political career. Obama and Ayers live in the same Chicago neighborhood and served on a charity board together, but there is no evidence they have palled around.
Rep. Rahm Emanuel, a Chicago Democrat and Obama supporter, warned against McCain's strategy.
"If we are going to go down this road, you know, Barack Obama was eight years old, somehow responsible for Bill Ayers," he said. "At 58, John McCain was associating with Charles Keating."
"If we really want to talk who is associating with who, we will," Emanuel said. "The American people will lose in that transaction."
Just months into his Senate career, in the late 1980s, McCain made what he has called "the worst mistake of my life." He participated in two meetings with banking regulators on behalf of Keating, a friend, campaign contributor and S&L financier who was later convicted of securities fraud.
The Senate ethics committee investigated five senators' relationships with Keating. It cited McCain for a lesser role than the others, but faulted his "poor judgment."
In the new Obama ad, an announcer says: "Our financial system in turmoil. And John McCain? Erratic in a crisis. Out of touch on the economy."
The ad, slated to start running Monday on national cable, alludes to McCain's response to the nation's financial crisis. He briefly suspended his campaign, called for a White House summit meeting that ended chaotically, and showed varying degrees of support for the massive rescue bill Congress passed Friday.
Republicans say McCain's actions showed leadership.
"In the midst of it all, I think you saw Sen. McCain, unlike Sen. Obama, come off the campaign trail, because that's John McCain in the middle of a crisis," said Sen. Joseph Lieberman of Connecticut, an independent-Democrat who backs McCain.
Associated Press reporters Stephen Ohlemacher and Mike Baker contributed to this report.
On The Net: Obama ad: http://my.barackobama.com/page/content/thisyear-ad/