PORTLAND – Amid differences on big issues such as Iraq, health care and the economy, the latest exchanges between Republican Sen. Susan Collins and Democratic challenger Tom Allen focus not on how they voted but how often.

In speeches and media interviews, Collins has been taking Allen to task for his missed votes in what she says is a reflection on his work ethic and his commitment to his job.

“Tom has missed 135 votes. And yes, I’m counting. That is more than the rest of the Maine delegation added together and tripled,” Collins told a Lincoln Day dinner last month in Lewiston.

Allen said her claim that his missed votes represent lack of commitment runs counter to the Maine tradition of congressional delegation members working as a team on vital issues such as the 2005 round of military base closings. He also said she’s trying to deflect attention from her own voting record.

Not everyone is convinced that absences during roll calls make much of a difference.

“Chances are, many of the missed votes didn’t affect the state and were on fairly routine and unimportant matters,” said Ross Baker, a political science professor at Rutgers University.

The race between Allen, a six-term congressman, and Collins, the two-term incumbent, is seen by Democrats as one of their best opportunities to oust a Republican this fall.

Collins is portraying herself as a moderate with a history of bipartisanship while Allen says she sides too often with President Bush and is out of sync with the views of most Maine voters.

It’s no surprise that Collins is raising the issue of roll-call votes. She prides herself on never having missed a roll call during her more than 11 years in the Senate – a Cal Ripken-like feat that recalls the record set by the late senator who inspired Collins’ political career, Margaret Chase Smith.

In 2005, Collins broke Smith’s record of 2,941 votes, a 13-year streak that ended when she underwent hip surgery. Collins’ record at last count stood at 3,764.

“The mere fact that she has perfect attendance is a great issue that speaks to her work ethic,” Collins’ campaign manager, Steve Abbott, told The Associated Press. “[Allen] has an obvious weak spot there, which is his failure to show up for work on many different occasions.”

Reasons for Allen’s missed votes, according to the Collins campaign, included a campaign fundraising trip and a visit to Fenway Park to attend the 1999 All-Star game.

Baker said missed votes are often cited as evidence of lack of attentiveness. “Because Margaret Chase Smith prided herself on that record, it’s probably a more prominent issue in Maine than it might be in other places,” he said.

“But there’s always a very potent response, and that is that the person is absent because he’s back in the state, doing more important things,” Baker said.

During the 110th Congress, Collins is one of 10 senators – including fellow Maine Republican Olympia Snowe – with a 100 percent voting record. The Senate average is 95.2 percent, according to a database compiled by The Washington Post.

Allen’s 96.8 percent attendance for the session is slightly below what he says is his 98 percent career record but still above the House average for the session of 95.6 percent. His campaign also says he has cast a total of 7,019 career votes in the House, where members vote more often than in the Senate.

Though he ranks in last place for roll-call votes among Maine’s delegation, Allen said 98 percent attendance is nothing to sneeze at. As for the missed votes, he said some of those occurred when his parents were dying, when he attended a relative’s funeral and when his wife recently was diagnosed with breast cancer and underwent surgery. There also were times when he missed a flight.

“I take my voting attendance very seriously,” he said. “Ninety-eight percent over 11 1/2 years is something I have a right to be proud of.”