A guessing game is in full force in Canada-U.S. circles about his replacement, with many prognosticators believing U.S. President Barack Obama might send a woman to Ottawa for the first time in history.
Among the names with the most buzz are Christine Gregoire, the former governor of Washington state who's played a key role in the Beyond the Border agreement between the U.S. and Canada; Jennifer Granholm, the Canadian-born former governor of Michigan; and Olympia Snowe, the long-serving Republican senator from Maine who opted against running for office in November, fed up with partisan gridlock.
The moderate Snowe, incidentally, isn't the only retired Republican senator at the centre of ambassadorial rumours. Some are speculating former Texas lawmaker Kay Bailey Hutchison might also be in the running for ambassador to Mexico.
The Canadian ambassadorship is a coveted one in diplomatic circles.
"Canada is considered a plum diplomatic post and history tells us the president uses that post to reward folks who have been major supporters, who have his ear and his confidence," says Christy Cox, a senior adviser to David Wilkins, who served as U.S. ambassador to Canada from 2005 to 2009.
"So whomever does get it will be someone the president both likes and trusts."
One of the Obama campaign's 2012 field organizers publicly went to bat for the Vancouver-born Granholm upon news of Jacobson's imminent departure.
"I expect to see Jennifer Granholm, the former two-term governor of Michigan and Current TV host, selected to serve in the Obama administration," Adam Silbert, a New York lawyer and Obama fundraiser, wrote in a letter to the Vancouver Sun.
"President Obama has received criticism in the press for a string of male appointments for his second term. If Granholm is chosen, I'd hope a lead about gender would not overshadow her distinguished career."
Granholm, whose brother serves in the Canadian military, is one of Obama's biggest public cheerleaders. She delivered a rousing speech about the president at the Democratic National Convention in September.
In an interview shortly after his inauguration last week, Granholm spoke of her pride as she took in his inaugural address.
"That he would make two reference to the rights of gay Americans in an inaugural address was so groundbreaking ... and yet it's who he is, it's who we are. He's bringing the issue into the mainstream," said Granholm, who's also rumoured to be in the running for a cabinet position.
"That's why I just so admire our president ... he's the progressive Ronald Reagan, he really is, and he's putting liberalism back into the mainstream and making us proud."
Granholm has been coy about the ambassadorial speculation.
"I am evaluating a lot of things right now," she said.
"I am looking at a lot of interesting things, so stay tuned. But obviously I'm always interested in serving, and I'm interested in serving our president in whatever capacity he'd like me to serve."
Chris Sands, a Canada-U.S. relations expert at the Hudson Institute in Washington, suggested two other names that would shock and awe Canadians: Susan Rice, currently the U.S. ambassador to the United Nations, and Caroline Kennedy, daughter of John F. Kennedy.
The Kennedy pick could happen if John Kerry, the new secretary of state, has a say in the selection, Sands said.
Kerry is close to the Kennedys and Caroline Kennedy was said to have been wounded by the rough ride she got from the media after announcing in December 2008 that she wanted to make a run for Hillary Clinton's Senate seat. She withdrew her name from consideration a month later.
"If she was looking for a job, not only would Canadians love it but it would be a great gesture from the Obama administration to offer her that type of position," Sands said.
Rice, who's married to a one-time CBC producer, is also said to be feeling beat up after Republicans dashed her hopes of replacing Hillary Clinton at the State Department because of her public comments about the attack on the American consulate in Benghazi in September.
"She was battered in terms of Benghazi, so the president may want to give her a nice post and Benghazi, I don't think, would cause any problems for that appointment," Sands said.
"She'd be the double win because she's a woman and African-American, and if she indicated she wanted to leave the UN, that might be a feasible choice."
Rice would also be a fascinating pick given the federal Conservative government's anti-United Nations bent in recent years.
The 65-year-old Snowe, however, seems a particularly "believable" choice given both Granholm and Gregoire are in the running for cabinet positions, Sands added.
"She's the kind of Republican Obama feels comfortable with, so he could very well go that route."
But David Biette, director of the Canada Institute at the Wilson Centre think tank in D.C., believes the next ambassador will be a relative unknown, chosen from a coterie of Obama loyalists who helped raise major money for his 2012 campaign — much like Jacobson.
"The question is who gave a lot of money, who was one of the big bundlers, who does he owe favours to? That's where the next ambassador will come from," he said.
"It will be another loyal soldier, and probably not someone with a lot of name recognition."
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