Maine Democrats and Republicans continued to squabble Monday over John McCain’s campaign effort to raise questions about Barack Obama’s relationship with a 1960s radical.

Obama’s connection to Bill Ayers was highlighted in automated telephone calls to some Maine homes last week from McCain’s GOP presidential campaign and the Republican National Committee, and also in a flier mailed out by the Maine Republican Party.

The flier features police mug shots of Ayers, a former fugitive and neighbor of the Illinois senator who was involved in several bombings in the 1970s, and describes him as “Terrorist. Radical. Friend of Obama.”

As a campaign tactic, the so-called “robo-calls” and mailing were part of a national effort by McCain and the Republican Party to maintain a focus on Obama’s trustworthiness and character. Similar automated calls were reported in Virginia, North Carolina and several other states last week.

The mailing, received in some Maine homes over the weekend, prompted the Maine Democratic Party to renew its call Monday for U.S. Sen. Susan Collins to resign as co-chairwoman of the McCain campaign in Maine. Democrats also said Collins should seek the resignation of state Republican Party Chairman Mark Ellis.

“This is the most hideous example of dirty campaigning we’ve seen in Maine in recent memory,” said Rebecca Pollard, the Democratic Party spokeswoman.

The Collins campaign did not return several phone calls seeking comment Monday. The campaign spoke out against the calls last Friday, after Democrats first pressed her to take a position.

“These kind of tactics have no place in Maine politics,” Collins spokesman Kevin Kelley said on Friday. “Sen. Collins urges the McCain campaign to stop these calls immediately.”

Collins, who is running for re-election to a third term against Democratic U.S. Rep. Tom Allen, has often been critical of negative campaigning.

Ellis, the state GOP chairman, was out of state Monday and could not be reached for comment. In a statement issued by the party, he said, “Obama’s connection to an unrepentant domestic terrorist like Bill Ayers is raising red flags across Maine and the nation. … That’s why the Obama campaign and the Democrats are so alarmed, they can’t defend this troubling relationship that raises serious questions about Senator Obama’s judgment.”

But other Maine Republicans were critical of the McCain efforts.

U.S. Sen. Olympia Snowe, a Republican who is a co-chairman of the Arizona senator’s campaign in Maine, issued a statement against the calls and flier through a spokesman Monday.

“She feels they are regrettable and inappropriate, and these tactics should be suspended immediately,” said John Richter, Snowe’s chief of staff.

He said Snowe “will be in contact with the McCain campaign to express that directly.”

Charlie Summers, a Republican running against Democrat Chellie Pingree for the congressional seat now held by Allen, also said Monday he was opposed to the robo-calls.

“People want members of Congress to do what’s right for the country and set this bickering aside, and this does not help the process at all,” Summers said.

Ayers, the object of the calls and flier, has been the focus of a persistent McCain effort to raise questions about the character and judgment of Obama, the Democratic presidential nominee.

The co-founder of the radical left Weather Underground in 1969, Ayers is now a University of Chicago education professor. He served on two community boards of directors with Obama from 2000-2002 and once hosted a luncheon fundraiser at his home for Obama, when he ran for the Illinois state Senate in 1995.

Obama has disputed suggestions that he and Ayers are close, saying that he does not know Ayers well and that he was only 8 years old when Ayers was engaging in domestic bombings in the 1970s.

Mainers began getting automated phone calls about Ayers and Obama last Thursday, after the final presidential debate between Obama and McCain. The 30-second call, recorded by a male announcer, states that voters “need to know that Barack Obama has worked closely with domestic terrorist Bill Ayers.”

The calls, some with different scripts, were also reported in several other states across the country.

McCain told a reporter at WCSH-TV in a satellite interview Sunday that the ads are factual and that Obama has been “untruthful” about his relationship with Ayers.

“I’m proud of our campaign,” McCain told the station. “I’m proud of how we’re doing, and I hope we’ll do well up there in Maine as well. We love the state.”

McCain’s New England press office issued a statement Monday contending that the GOP candidate has himself been the object of numerous “extreme attacks” by Obama or his supporters.

They have accused John McCain of “losing his bearings,” of “erratic behavior,” of “sowing the seeds of hatred and division” and of being a “warmonger,” the McCain campaign said, and Obama has not repudiated any of those statements.

“These comments are outrageous and have been divisive to this race,” the campaign said.