West Virginia Senator Robert C. Byrd's evolution from gay rights foe to supporter of allowing gay troops to serve openly is being hailed by gay rights groups after the senator's demise.

Byrd, the longest serving senator in history, died Monday at the age of 92.

The Democrat served 51 years in the Senate and was considered the chamber's unquestioned expert on its complicated rules and procedures.

He first came to Washington as a member of the House - in 1952 – where he served three terms before moving on to the Senate.

Byrd once sought his party's presidential nomination, in 1976.

Byrd slowly renounced his objections to gay rights, going from supporting “Don't Ask, Don't Tell,” the law that forbids gay troops from serving openly, and opposing gay marriage in the 90's to backing a measure last month that repeals the military's gay ban.

In 1996, as the Senate debated the Defense of Marriage Act (DOMA), a law that defines marriage as a heterosexual union for the federal government, he called gay marriage “an effort to make a sneak attack on society by encoding this aberrant behavior in legal form before society itself has decided it should be legal.”

In a statement released Monday, Aubrey Sarvis, executive director of Servicemembers Legal Defense Network, a group that lobbies for DADT repeal, praised Byrd for his evolution on gay rights.

“Senator Robert Byrd achieved much for his state of West Virginia and the nation,” Sarvis said. “Some of his votes over the years were controversial and not where most Americans stood. But Senator Byrd evolved in his thinking on 'Don't Ask, Don't Tell,' as did our country.”

As a member of the Senate Armed Services Committee, Byrd voted in favor last month of attaching language that repeals the gay ban to the military's 2011 defense budget. The full Senate is expected to vote on the bill next month. Republicans have threatened to filibuster the bill.

“We hope the new senator from West Virginia will follow the lead of Senator Byrd on the issue,” Sarvis added.

Byrd's body will lie Thursday in repose in the Senate chamber.