Senator Hillary Rodham Clinton remains a polarizing figure amid swirling speculation about her presidential ambitions. But a new book says her biggest strength going into a national campaign could be her ability to find a middle path.

McGill University presidential historian and author Gil Troy writes in his new book "Hillary Rodham Clinton: Polarizing First Lady" that she continues to be a divisive figure nearly six years after she left the White House as first lady.

"There are people who love Hillary Clinton, there are people who hate Hillary Clinton. It's very, very hard for her to change people's opinions even though she has been a senator for (several) years," he told CTV's Canada AM.

Calling her the "rollercoaster first lady," Troy said her transition from first lady to senator has been a remarkable one.

"It was quite extraordinary how she went from really being one of the most hated figures in American politics during those first six months in office to being able to pull off an amazing transformation and ending up in the Senate," Troy said.

"No one expected her to end up in the Senate. It was farfetched when people first started to talk about it and the fact that she was able to do it shows her determination, shows her focus, and it shows her ability to find a connection with a significant group of Americans."

Her turning point may in fact have come at one of the most painful times in her marriage, when her husband admitted he had an affair with White House intern Monica Lewinsky.

"One of the great tragedies of Hillary Clinton's life, especially as first lady, was that when she was in her 'Helen Reddy, I am feminist, I am woman, hear me roar phase,' it was very hard for her to be popular with the public " Troy said.

"But when she was in the wronged wife approach, when she seemed much more of a victim, that's when she became popular. She seemed much more of a traditional housewife rather than a cutting-edge change agent. So the problem for her was how can she appeal to the American people on her terms, and as senator, she's been able to do that.

Troy dismissed speculation the Clintons' marriage was simply a power relationship driven by political ambitions.

"It seems quite clear to me that all the cynical conjecture that the Clintons just had a power relationship ... doesn't make sense considering that she moved all the way to Arkansas from the East Coast in order to follow her man, in order to follow her heart, in order to establish her relationship and her marriage with Bill Clinton -- so I think they do have a bond," Troy said.

"I think as Bill Clinton confessed in that '60 Minutes' interview, he's caused pain in the marriage, it's had its ups and downs, but it's unfair and disrespectful to dismiss their relationship as a power alliance.

If Hillary Clinton does in fact run for president in 2008, her greatest strength will be her centrist position, Troy believes.

"She's much more of a centrist than people give her credit for, and when she's a centrist, it's not just some kind of posture to balance the red and the blue states, it comes from a very deep part of her biography," he said.

He explained that her polarizing impact becomes easier to understand considering she grew up as a 1950s Midwestern Methodist and then made her way through the feminist revolution of the 1960s.

"Her whole life she's been trying to balance. So when she talks about abortion being safe, legal and rare, it's not just a posture, it's something she's really been trying to show the yuppies, the baby boomers and the American people we can find a middle path and that's in some ways her greatest strength going into the campaign."

Clinton is currently mounting a major push for Democratic Congressional candidates across the nation during the final weeks of the fiercely contested midterm elections.

Among the places where she plans to rally for support are Ohio and Pennsylvania, two important presidential battleground states, where she will campaign for House and Senate Democratic candidates.

Her advisers say Clinton is motivated by her desire to strengthen her party's political prospects, but observers say this is also a ripe opportunity to gain favour among Democrats who could be lend a hand in a national campaign.