Washington - Five months ago, at the start of the US general election, much of the talk was of disaffected Hillary Clinton voters leaving the Democratic Party and throwing their weight behind Republican John McCain.

Female voters who backed Clinton's historic candidacy were enticed by McCain's selection of Alaska Governor Sarah Palin as a running mate. The McCain campaign also hoped working class voters who plumped for Clinton could be convinced to switch sides in a repeat of the 1980s elections that swung on so-called "Reagan Democrats."

Yet the buzz has more recently shifted in the other direction. With only two days to go to the general election, Democrat Barack Obama is leading opinion polls in part because of inroads made in traditionally Republican regions of the country.

The "Obamacans" bandwagon has also collected some prominent conservative endorsements.

Highest among them has been Colin Powell, the former secretary of state under President George W Bush and once considered a possible presidential candidate. Powell, who left the Bush administration over some foreign policy differences, endorsed Obama as a "transformational figure," in mid October after months of speculation.

On Friday, Ken Duberstein, a chief of staff under former president Ronald Reagan, told broadcaster CNN that he too would be voting for Obama. He cited Powell's endorsement as a factor in his decision.

Other defections include Scott McClellan, Bush's former press secretary, and Christopher Buckley, the son of the late noted US conservative icon William Buckley.

Buckley endorsed Obama last week and claimed he was promptly told to give up his back-page weekly column in the National Review, a weekly magazine started by his father.

Another surprising backer is Ken Adelman, a strong supporter of the US-led invasion of Iraq who has served in a number of Republican administrations. His complaint with McCain fell in part on his pick of Palin, Alaska's governor since 2006, who Adelman considered too inexperienced for the job.

McCain has also attracted some prominent defections. Early on in the campaign, Lynn Forester de Rothschild, a one-time Clinton fundraiser, left the Democratic National Committee to join the Republican campaign.

Parting ways with the Democratic camp more recently was Wendy Button, a former speech writer for Obama, Clinton and 2004 vice presidential candidate John Edwards. She complained of sexism in the campaign and the media's treatment of Palin in particular.

But perhaps most noteworthy has been Connecticut Senator Joe Lieberman, who was Democrat Al Gore's running mate in 2000. Lieberman, an independent since 2004, has been a regular on the campaign trail with McCain and spoke at the Republican nominating convention in September.

The departures arguably play to the candidates' strengths as post- partisan politicians. McCain has long had a reputation as a "maverick" senator unafraid of taking on his own party and working with Democrats on a number of key issues, including campaign finance reform, immigration and climate change.

Obama, for his part, often speaks to American voters' desire for both sides to come together. The most famous line of his 2004 Democratic convention speech that catapulted him into the political limelight was: "There is not a liberal America and a conservative America - there is the United States of America."

Among all voters, polls suggest there is a small group moving in either direction. According to a Gallup Poll, 10 per cent of Republicans will vote for Obama, and 9 per cent of Democrats will vote for McCain. (dpa)