Someone was conspicuously absent from the Connecticut delegation to the Democratic National Convention in Denver last week.

“I wish he were here,” Sen. Christopher Dodd told the News of his missing colleague, Sen. Joseph Lieberman ’64 LAW ’67.

Just eight years after running for vice president on the Democratic ticket, Lieberman has left the party and thrown his weight behind the Republican nominee, Sen. John McCain of Arizona. His participation in the Republican convention this week completes a political transformation that has stunned both Lieberman’s former allies and former classmates.

The Joseph Lieberman they knew, they said, would have supported Barack Obama.

“What, after all, is a Democrat like me doing at a Republican convention like this?” Lieberman said in his remarks at the Xcel Center in St. Paul, Minn., on Tuesday. “The answer is simple. I’m here to support John McCain because country matters more than party.”

Lieberman — who has accompanied McCain on several trips overseas since he clinched the Republican nomination — went on to say that he supports his friend because McCain has the ability to bridge partisan politics and get things done.

In some ways, Lieberman has long stood out as a Democrat, despite his progressive social stances, for his hawkish foreign-policy positions; indeed, when he first ran for Senate in 1988, he came at his incumbent opponent, Republican Lowell Weicker, from the right on several issues. But it was because of his continuing emphatic support for the unpopular war in Iraq that he ended up booted from his party and seeking re-election as an independent, on his very own Connecticut for Lieberman ticket.

The 2006 election, when Lieberman lost the Democratic primary, was the breaking point, but Lieberman’s slide to the right started long before, said his 2006 opponent for Senate in the Democratic primary and the general election, Ned Lamont SOM ’80. By that time, Lieberman was already far from the progressive, anti-war Democrat he was at Yale, Lamont said.

If asked when he was a Yale student, Lieberman would have identified himself as a Kennedy Democrat, said Jethro Lieberman ’64, a classmate and fellow News editor who is now a professor at New York Law School. The two men are not related, and Jethro Lieberman said they have not spoken in at least a year.

Like many in his generation, Joe Lieberman was swept up with the Kennedy Camelot, which energized young voters about the future of politics and public service.

“It was the same sort of feeling that young people have for [Sen. Barack] Obama these days,” Jethro Lieberman said. “Along comes someone who in some ways echoes that, and Joe’s not a part of it.”

As chairman of the News, Lieberman proclaimed his support for Kennedy, calling on Congress on March 12, 1963, to enact a “whole range of New Frontier programs.” He took his strongest liberal stances in his editorials on the sprouting Civil Rights Movement.

“The Joe that we knew was a JFK liberal Democrat,” said Robert Kaiser ’64, who was a News editor with Lieberman. “He would not have supported McCain.”

Kaiser, now an associate editor at The Washington Post, met Lieberman at the Democratic Party headquarters in New Haven, where they had both signed up as volunteers for Kennedy.

Lieberman’s commitment to the Democratic Party was as obvious as his intentions to secure his place in it, Kaiser said. For his senior essay, Lieberman wrote a “flattering portrait” of Connecticut’s Democratic political boss, which Kaiser said was Lieberman’s clear attempt to jumpstart his own political career.

“The Democratic Party was the entire world as far as he was concerned then,” Kaiser said.

Lieberman’s transition over the last 45 years or so may be easier to observe than to explain, Jethro Lieberman said. Perhaps the change was more political than ideological, he said. Or perhaps it’s not the person but the circumstances that have changed.

The Yale student who knew he would “make a home for himself in the Democratic Party” and did so shortly after graduating Law School, Jethro Lieberman said, has crossed over to the Republicans, at least for this presidential race. But how Joe Lieberman’s political trajectory may continue from there may be just as unpredictable, Jethro Lieberman said.

“The story is still unfolding,” he said.

Thomas Kaplan contributed reporting from Denver.

Contact isaac arnsdorf at isaac.arnsdorf@yale.edu