Snowe with John Chafee, right, in 1996

When Gov. Lincoln Chafee became a Republican U.S. senator in 1999, he ate lunch each week with four other GOP moderates: Olympia Snowe and Susan Collins of Maine, Jim Jeffords of Vermont and Arlen Specter of Pennsylvania. They called themselves “the Mod Squad.”

In 2001, Jeffords left the party to caucus with the Democrats. In 2006, Chafee lost his seat to Sheldon Whitehouse after a primary challenge from the right. In 2009, Specter switched parties and went on to lose his first Democratic primary. And on Tuesday, Snowe shocked Washington by announcing her retirement.

“Of the five members of the ‘Mod Squad,’ soon only one will remain a U.S. senator, and that says a great deal about the ways in which Washington and the Republican Party have changed,” Chafee told WPRI.com in a statement. The last remaining member is Collins, who was re-elected in 2008.

Snowe said Tuesday she had been planning to run again in November and thought she would win. “However, what I have had to consider is how productive an additional term would be,” she said. “Unfortunately, I do not realistically expect the partisanship of recent years in the Senate to change over the short term.”

Chafee expressed sympathy for Snowe’s predicament. ”The demanding job of being in Congress has been made infinitely more difficult by the partisan climate to which Senator Snowe referred in her announcement,” he said. “I can certainly understand her decision.”

Snowe and Chafee weren’t always on the same side of big issues when they served together from 1999 to 2006. The governor frequently notes he was the only Republican who voted against the Iraq war and one of two who voted against the Bush tax cuts; Snowe supported each measure.

But both Snowe and Chafee were members of the so-called “Gang of 14,” an ad hoc bipartisan group of senators who brokered a compromise on judicial nominations in May 2005 to avoid a showdown over Democrats’ use of the filibuster against President Bush’s nominees.

“As members of the ‘Gang of 14,’ it was my pleasure to work with Senator Snowe to forge compromise and resist the increasing polarization of the Senate,” Chafee said.

In his memoir, Chafee recalled unsuccessfully trying to convince Snowe to join him in voting against the confirmation of Samuel Alito to the Supreme Court in early 2006 in light of her support for abortion rights. Chafee said she called him the night before he announced his opposition to say the Republican Party in Maine would challenge her in the primary that year if she opposed it.

Chafee called it “an excruciating decision” for Snowe, particularly since her vote would not have kept Alito off the bench and Maine has closed primaries. “In the end, Olympia had no primary,” he wrote. “Because she was strong and well financed, Democrats declined to actively engage her. She coasted to victory in a year that was abysmal for Republicans, and an utter rout in the Northeast.”

• Related: When Chafee backed Romney in the New Hampshire primary (Jan. 10)

(photo: Denis Paquin/AP)