"These kind of tactics have no place in Maine politics," Collins spokesman Kevin Kelley said. "Sen. Collins urges the McCain campaign to stop these calls immediately."
Coleman, in a tight re-election campaign, said he hoped all candidates and outside groups would stop their attacks.
In Nevada, a four-page campaign flier mailed this week by the state Republican Party also focused on Obama's past relationship with former Weather Underground leader Bill Ayers, calling the college professor a "terrorist, radical, friend of Obama" and featuring several images of Obama and Ayers.
Reid told reporters at a news conference in Las Vegas that he's surprised at the "scummy" tactics employed by McCain's presidential campaign and "can't believe John McCain knows what's going on."
The McCain campaign says the calls are warranted because Obama's connection to Ayers - the two met many years after Ayers' anti-Vietnam War activities had ended - raises questions about the Democrat's judgment and record.
"This is an association that is highly questionable and not out of bounds," McCain spokesman Rick Gorka said.
The automated calls in Maine, Nevada and other states - they are commonly known as "robo calls" - say Obama "has worked closely with domestic terrorist Bill Ayers, whose organization bombed the U.S. Capitol, the Pentagon, a judge's home and killed Americans."
The charge is misleading: The bombings, which took place more than 35 years ago, didn't result in fatalities and the group didn't claim responsibility for the attack on the judge's home.
Obama has condemned Ayers' radical activities, which took place in the late 1960s and the 1970s, when Obama was a child. In the debate Wednesday with McCain, Obama said Ayers played no role in his presidential campaign.
Ayers, an education professor at the University of Illinois at Chicago, lives in Obama's neighborhood in Chicago. In 1995, he hosted a meet-the-candidate session at his home as the young Harvard Law School graduate prepared to run for the Illinois Senate. The two also worked with two nonprofit charitable organizations in Chicago.
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