AUGUSTA — Maine Sen. Olympia Snowe’s surprise decision to retire has focused national attention on the partisan divide that she says is crippling America’s political system.

A Maine Sunday Telegram analysis of congressional voting records going back 30 years shows just what she is talking about.

It also shows that Snowe may be among the last of a vanishing breed.

Data obtained from voteview.com, a nonpartisan website that tracks congressional voting records, show a 63 percent decline in the number of U.S. senators willing to vote across party lines during the last three decades. The erosion of the political center is even more dramatic in the House of Representatives, where the number of centrist members dropped 84 percent during the same period.

The divide has been growing for decades as Democrats and Republicans have become less willing to compromise, and moderates from both parties have either dropped out or grown very lonely.

The two remaining centrists in the Senate – Snowe and Sen. Ben Nelson, D-Nebraska – both have decided to retire this year.

The trend is now pushing Congress to a breaking point, some political scientists say.

Polarization also has shown its effects in Maine. Snowe – one of the state’s most popular politicians ever and considered a shoo-in for another term – was facing a conservative primary challenger and getting booed at recent Republican caucuses for being too willing to compromise.

“She’s tough,” said former Maine Sen. Peter Mills, a moderate Republican who is now director of the Maine Turnpike Authority. “My guess is she’s thinking I can handle this (opposition) at home and get down there again, but what am I going to do when I get down there?”

Snowe said Friday that the Senate is no longer a place for consensus and compromise.

“We are becoming more like a parliamentary system, where everyone simply votes with their party and those in charge employ every possible tactic to block the other side,” Snowe said Friday. “At some point you have to develop solutions for the country. You have to talk to people with whom you disagree.”

Snowe’s retirement has highlighted a trend that University of Georgia political science Professor Keith Poole has been tracking for 30 years. He helped create a computer program that shows Congress is more polarized now than at any time since Reconstruction, the result of issues such as race, morality and economics that have pulled the parties apart in recent decades.

“The country is basically becoming fundamentally dysfunctional due to this polarization, and people are finally starting to notice,” Poole said. “It has to stop at some point. It has to break. I think we’re getting close.”

Snowe has voted with her party most of the time, including on contentious issues such as the national health care reform law of 2010.

But she negotiated with Democrats on health care reform when other Republicans would not and she frequently crosses the aisle, just last week becoming the only Republican to vote to uphold a requirement that non-church employers provide health insurance coverage for contraceptives.

Snowe had a lot of company as a moderate in Congress when she was first elected 34 years ago to the House of Representatives. Eleven of the 100 members of the Senate were classified as centrists in 1980, compared with three in 2010, according to Poole’s data. During that same time frame in the House, that number has gone from 49 centrist members to just 8.

The retirement this year of Snowe and Nelson, as it turns out, is likely to leave Maine’s junior senator, Republican Susan Collins, as the Senate’s most moderate member, the data show. The third centrist in 2010, Arlen Specter, D-Pa., is no longer in office.

Collins on Friday echoed Snowe’s criticism of the political atmosphere.

“It’s the most partisan that I’ve ever seen and it is preventing us from tackling the real issues in the Senate,” she said during an interview at the Portland International Jetport. “People in the middle who brought people together were applauded, and now we’re vilified.”

Collins votes with fellow Republicans slightly more often than Snowe does, according to Poole’s data. Last week, for example, she voted to allow employers a way out of the contraceptive mandate.

But Collins is still among the senators most likely to compromise with Democrats. A refusal to compromise is the reason Congress’ approval rating among voters is about 10 percent, and may be headed lower, she said. “I don’t even know who those 10 percent are.”

There have always been complaints about partisanship paralyzing Congress, said Mark Brewer, a political scientist at the University of Maine. The system is built on partisanship. But, he agreed, there is more evidence now that the complaints are valid.

“In the past I’ve been dismissive of that, (but) not anymore,” he said. “If you go back to 2006 … things are not getting done. Something is going to have to give.”

Brewer said that doesn’t mean a third party will necessarily emerge. It may mean that political leaders decide to compromise, or voters begin to demand that they do, he said.

“This is being reinforced from the bottom up. Americans have become increasingly well-sorted into their proper parties,” he said.

Maine has resisted the trend more than much of the country has, which helps explain why it is the last state to have two moderate Republican senators. Polarization is clearly happening here now, however, Brewer said.

“The biggest part of the Maine electorate is still the pragmatic middle. But, are the left wing and the right wing getting bigger? I think they definitely are,” Brewer said.

The conservative shift within Snowe’s Republican Party has been especially easy to see in the past five years.

In 2010, tea party activists surprised Maine party leaders by adopting a GOP platform that called for an investigation of “the global warming myth” and an audit of the Federal Reserve.

Paul LePage used tea party support to win the Republican nomination that June and then the governor’s office in November 2010. Last year, meanwhile, conservatives in the party took aim at Snowe and her record of compromise.

Had she stayed in, Snowe would have faced her first primary opponent in her 34-year congressional career.

And the woman who won her last election with more than 70 percent of the vote got booed last month when a representative stood up to support her at the Androscoggin County Republican caucus.

Mills said he was surprised to hear the boos and stood up to remind fellow party members why they needed Snowe at the top of the ticket.

“I said, ‘Let me tell you about her. She’s going to run and she’s going to get 70 percent of the vote,’ ” Mills said.

Snowe’s retirement decision not only takes her off the party’s ticket. It also is sure to leave the U.S. Senate more polarized, at least temporarily.

“In the long run, her resignation may carry with it such a powerful message that it may carry the country back,” Mills said.

Staff Writer Edward D. Murphy contributed to this report.

MaineToday Media State House Writer John Richardson can be contacted at 620-7016 or at:

jrichardson@mainetoday.com