Liberal MP Bill Graham rose today in the House of Commons and formally announced his resignation, effective July 2, clearing the way for Bob Rae to run in the riding of Toronto Centre in a byelection.

Graham, a party stalwart who commands respect from all sides in the House of Commons, was first elected in 1993 -- after two unsuccessful tries -- and served as minister of foreign affairs and later national defence. He also served as the party's interim leader for almost an entire year after the 2006 election.

"I'd like to say a few words about having the privilege to be elected to one of the best parliaments in the world," said a tearful Graham after receiving a standing ovation from his fellow MPs.

"It's an enormous privilege to sit in this House, it's very difficult to think I will no longer have access to a place that is so sacred to all of us."

Tributes poured in from all sides of the House of Commons.

"This House has surely been better" for Graham's presence, said Liberal Leader Stephane Dion.

He credited Graham with being a strong voice around the cabinet table in the debate over keeping Canada out of the Iraq war.

"The member for Toronto-Centre knew it was the right decision, and I am proud of him for it," Dion said.

Prime Minister Stephen Harper said he was pleased to salute Graham's career both inside and outside politics.

"He certainly had no need for the trials and tribulations of elected public office," Harper said. "But nevertheless, he took those on."

Graham conducted himself as interim opposition leader "with great intelligence, great passion and great integrity," he said.

On a light-hearted note, Harper recalled some of his clashes with Graham in the House.

"In that role, he and I disagreed about very many things. I recall that we disagreed about the various ways one should or not wear silk," he joked.

Last November, after Graham gently needled Harper in question period for posing in a silk robe at the APEC Summit, Harper replied: "Now, Mr. Speaker, I can add in terms of photo ops, there's a tradition at APEC to do pictures in traditional garbs. Unlike the leader of the opposition, I have to wear the silk on the outside."

Graham's riding includes the exclusive Rosedale neighbourhood in Toronto.

Graham announced in February that he wouldn't seek re-election. Numerous high-profile Liberals coveted his seat, considered one of the safest ridings in the country.

Graham held the seat by more than 14,000 votes over the second-place NDP candidate in the last election.

Liberal sources have said both Rae and Martha Hall Findlay, another leadership candidate, wanted the seat. Rae ended up getting the nomination.

Hall Findlay has been appointed the Liberal candidate in Willowdale. Ex-cabinet minister Jim Peterson has already announced he will not seek re-election there.

Byelection politics

The announcement comes as some recent polls indicate that the Conservative party appears to be sagging slightly in popularity.

"So Liberal strategists have been saying, 'What do we do in the coming months to give ourselves the appearance of having some momentum,'" said CTV's chief parliamentary correspondent Craig Oliver.

"Well one thing they came up with was to ask a couple of their MPs, who had already planned to retire, to do so earlier than the next election and open byelections -- which Liberals believe that they can win."

Graham asked Harper to call a byelection as soon as possible for his riding.

The prime minister has a six-month window of opportunity for any particular byelection.

He must call a vote in Montreal's Outremont riding by July 28, where NDP star candidate Thomas Mulclair is considering running. Some think he will call byelections at the same time for some other vacant Quebec ridings.

The Liberals hope the Tories call the Graham byelection at that time.

Besides Peterson's retirement, Vancouver Liberal MP Stephen Owen will also be leaving politics.

The Prime Minister's Office has said that dates haven't yet been determined for the three Quebec ridings.

"There's obviously a number of vacancies that have to be filled, and one of the problems that the prime minister's had in terms of when to call these byelections is we also know there are some coming," said Peter Van Loan, the Conservative house leader, on CTV Newsnet's Mike Duffy Live.

But in the case of Bloc MP Michel Gauthier's Roberval riding, the Bloc has indicated he's resigning at the end of the session, but it's not yet official, Van Loan said.

Politically, these byelections are "a zero-risk proposition for us," because the seats are all currently held by opposition MPs, he said.

On Monday, Conservative MP Myron Thompson, originally elected in 1993 under the Reform party banner, announced he won't be running again in his Wild Rose riding in Alberta. However, the 72-year-old will stay on as an MP until the next election.

With files from The Canadian Press