Toronto MP Bob Rae put aside his personal ambitions and dropped out of the Liberal leadership race on Tuesday, assuring rival Michael Ignatieff's ascension to the party's top job.

Liberal MP Bob Rae arrives at his Toronto office on Monday before speaking to reporters about the leadership selection process. (Chris Young/Canadian Press)

The former Ontario NDP premier said Canada has experienced extraordinary events that have changed the political landscape since he joined the contest two months ago.

Rae said it's essential that the party have a permanent leader in place before Parliament reconvenes in late January, when key confidence votes could trigger the fall of Stephen Harper's minority Conservative government.

"I think we all have to accept that the flow of events in this last while have been quite extraordinary and our own ambitions are less important than the greater interest of the Liberal party and the greater interest of the country," Rae said at a news conference in Ottawa.

The party was originally slated to select a replacement for embattled leader Stéphane Dion at a spring convention in Vancouver, but quickened its search after Harper moved to suspend Parliament to avoid losing a confidence vote.

"I think the executive was under a lot of pressure," Rae told CBC News later in the day. "We had to find a quick resolution of the issue."

The April 29-May 3 convention will now likely serve to officially confirm Ignatieff as the permanent leader, though he is expected to take over from Dion as interim leader within the next few weeks. Under the party executive's constitution, a convention must be held to choose a permanent leader.

Ignatieff offers thanks, praise

Late in the day Ignatieff issued a statement acknowledging Rae's years of public service and his friendship.

"Bob Rae has dedicated his life to serving Canadians and I have always felt privileged to count him as a friend and colleague," Ignatieff said in the statement.

"I am grateful for his support and I look forward to continuing the work of rebuilding the Liberal party with him, and all Liberals, in the weeks and months ahead."

Rae said he made the "easy and obvious" decision to withdraw from the contest on Tuesday morning when he learned of the Liberal party executive's decision to open the leadership selection process to about 800 party officials.

Michael Ignatieff, right, signs Dominic LeBlanc's Liberal leadership nomination form on Nov. 16. LeBlanc dropped out of the race and threw his support behind Ignatieff on Monday. (Chris Young/Canadian Press)

Over the last week, Rae had been fighting for the leadership vote to be open to all party members.

Even though he resolved to accept the party executive's decision "without any bitterness," Rae said he will continue to push for changes to a one-person, one-vote system for future leadership contests.

But he did offer his "full and unqualified" support to Ignatieff and sang his praises, saying his fellow Toronto MP would prove a "formidable leader."

"I know Michael Ignatieff to be a person of wisdom and to be a person of generosity. He will make a great prime minister," said Rae.

He also described Ignatieff, whom he has known for decades, as a compassionate man with a "remarkable" network of friends around the world and a deep love for his country.

Rae urged supporters to back Ignatieff and said his selection as leader would be "entirely constitutional, legitimate and appropriate."

The Grits are eager to install a new chief before Parliament resumes Jan. 26, to give the party more stability before the Conservatives introduce their annual budget, and a confidence vote that could send Canadians to the polls or see the rise of a proposed Liberal-NDP coalition.

Party not divided: Rae

Rae's announcement comes a day after the only other candidate, New Brunswick MP Dominic LeBlanc, stepped out of the race and threw his support behind Ignatieff.

Also Monday, Dion declared he would step down earlier than the leadership convention in five months, making way for a leader as soon as one was chosen.

By bowing out, Rae said he hoped to ensure Ignatieff was the undisputed and unanimous choice of the party, dispelling talk that the party is divided.

"Frankly, a political contest between the two or three or however many of us, that would just continue to give people the impression that we're divided," said Rae.

"I thought I had a shot at winning the leadership, and we came pretty close this time and last time," he told CBC.

Rae said that he had not spoken to Ignatieff before his news conference, eliminating suggestions he orchestrated a backroom deal with his friend and leadership rival.

Ignatieff was lying low on Tuesday and not available for public comment, but was expected to speak after the Liberal caucus meets on Wednesday.

On his website, however, he did express gratitude for Rae's decision, writing, "His decision today reflects his commitment to the unity of our party and our purpose in these challenging times."

Rae dismissed questions about whether he was upset by his second failed bid for the federal Liberal leadership. "It's just politics," he told reporters. "It's not the end of the world here, folks."

NDP fear coalition collapse

With Ignatieff poised to take the helm of the party, some New Democrat MPs were privately worried that the Liberal-NDP coalition could collapse, CBC's Rosemary Barton said.

While Rae was supportive of the coalition set up to topple Stephen Harper's government, Ignatieff appeared lukewarm to the pact.

Over the weekend, he summarized his position as "coalition if necessary, but not necessarily coalition," echoing former prime minister William Lyon Mackenzie King's fence-sitting position on conscription.

At Tuesday's news conference, Rae, however, reiterated his staunch support for the coalition.

"We have a political and even moral obligation to replace this government, a government that has shown a lack of ability with respect to the economy and the Canadian people … and an inability, a total inability to work with other parties."

New Democrat MP Olivia Chow insisted that it doesn't matter who ascends to the top Liberal job.

"What's necessary is that Mr. Harper cannot be trusted. We have a very good plan," she told CBC News.

"I hope that all of the Liberal caucus after tomorrow's caucus meeting can join with us to go across the country and say that we have a plan, the plan works and we must make sure that this plan is implemented."

The creation of the coalition was triggered by widespread frustration among opposition parties with the government's fiscal update.

In late November, Finance Minister Jim Flaherty's update proposed to ditch per-vote public funding of political parties and freeze public servants' right to strike for three years. It didn't include a stimulus package for the slumping economy.

With files from the Canadian Press