U.S. Democratic presidential hopeful Hillary Clinton may be developing an exit strategy that includes angling to become Barack Obama's running mate, says her biographer.

Carl Bernstein told CTV's Question Period on Sunday that despite the Clinton camp's brave words, frontrunner Obama will become the Democratic nominee -- "unless something catastrophic happens."

Obama, a rookie Illinois senator, has the support of 1,865 delegates in primaries held since January. He needs 2,025 to secure his party's nomination.

Clinton is behind with 1,697 delegates, and she's lost her once-formidable lead amongst superdelegates, senior party officials who get an automatic right to vote and aren't obligated to support any candidate in particular.

The New York senator still insists she's in the race to win. But Bernstein said his sources tell him that Clinton and her husband Bill, a two-term president of the United States, are looking for ways to "land the plane."

But Bernstein suggests the Obama camp may not see her as an asset, adding, "the question is can she bring enough to the ticket to help beat John McCain?"

McCain, an Arizona senator, is the Republican Party's presumptive nominee.

Clinton outperformed Obama in large states like California and Ohio, which could be an asset if she joined the Democratic ticket. She has held an edge among blue-collar white voters, latinos and older women, while Obama's core constituency is among the young, blacks, and affluent whites.

"His fear is could she be a drag on the ticket compared to some other people," Bernstein said.

Clinton is a polarizing figure in American politics. In polls, at least 40 per cent of Americans have said they wouldn't vote for her under any circumstances.

The worst

Bernstein -- author of the 2007 book "A Woman In Charge" and one-half of the famed Washington Post reporting duo "(Bob) Woodward and Bernstein" that reported the Watergate scandal in the 1970s -- said this tightly contested nomination fight seems to have brought out the worst in Clinton.

"In this campaign, we have seen a real devolution to the Hillary Clinton of the worst of the White House years, in terms of a lack of truthfulness, in terms of being willing to do almost anything or say anything to win," he said.

Her husband Bill was U.S. president from 1993 to 2001.

Bernstein said he's been surprised during this campaign about how often the Clintons have "played the race card," given how sensitive they have been to such issues in the past.

Just this past week, Hillary told The Associated Press: "Senator Obama's support among working, hard-working Americans, white Americans, is weakening again and how whites in both states who had not completed college were supporting me . . . There's a pattern emerging here."

Such comments have been seen as extremely divisive, especially since most analysts say Clinton cannot win the general election without the votes of African Americans, who generally support Obama.

"Some of the things Bill and Hillary have done in this campaign ... are really astonishing," Bernstein said.

Clinton may have erred by assuming her own inevitability as the nominee, and by being caught off-guard early in the campaign by Obama's victory in the Iowa caucuses.

However, "she started to go extremely negative. There started to be a fine line between truth and non-truth in her pronouncements," Bernstein said, adding many of her wins have been "ugly."

Still looking to win

The Clinton camp, while trying to angle for the vice-presidential slot on the ticket, is still looking to do some "carpet bombing" on Obama, he said, adding she can't win unless something catastrophic happens to the front-runner.

The risk in that approach is further angering the superdelegates who are her only real hope and the possible risk of the Clinton legacy within the Democratic Party, he said.

Hillary's stock in the party had never been higher before this fight, he said.

Her work in the U.S. Senate had been highly regarded, and she had lost the image of stridency from her White House years, Bernstein said.

In his book, Bernstein said he thought Clinton had learned from her mistakes.

"I think I was wrong. She has developed back to the embattled, take-no-prisoners, trench warfare Hillary Clinton that we saw (back then)," he said.

"Now I think she will recognize she has to go back to being a little softer and gentler. And so does Bill."

It's in the Clintons' interests to "not be seen as pariahs," and many Democrats are starting to see them that way, he said.