Clinton has a commanding lead in the all-important delegate count and is marching toward the nomination despite a string of recent losses.

A pair of victories yesterday would halt her slide and help reverse the narrative that her campaign is showing significant weakness ahead of an almost certain November showdown between Clinton and Donald Trump, the Republican Party's presumptive nominee.

Though Clinton holds a slim poll lead, Sanders was gunning for victory in Kentucky, building on his win last week in neighboring West Virginia as he battles to keep his long-shot nomination bid alive.

The self-declared democratic socialist was leading 47.2 percent to 46.1 percent, with about 40 percent of precincts reporting.

West Virginia and Kentucky are linked to coal, as is much of Appalachia -- the largely white, long-struggling eastern US region where many feel they have been left behind in the lukewarm recovery from the 2007-2008 financial crisis.

Oregon in the Pacific northwest conducted its Democratic and Republican primaries yesterday. Polls there close at 8:00 pm (local time).

"We need your help today to win in Oregon and Kentucky," Sanders implored his 2.2 million Twitter followers, urging them to man phone banks and call voters.

Limited Oregon polling has indicated Clinton is ahead. In Kentucky, only Democrats were voting for presidential candidates; Republicans have already held a caucus here.

Clinton sees Kentucky as an opportunity to appeal to working-class white men -- a demographic where the former secretary of state has lagged behind both the celebrity billionaire Trump and Sanders.

John Spenlau, 28, speaking to AFP outside a voting station in rainy suburban Louisville, said he voted for Sanders because he represented the best hope for "continued change" and the fight against income inequality, among other problems.

"Hillary would be a more stable candidate but I think that Bernie continues to push the envelope, towards a few more of the social programs that I believe in," Spenlau said.

Clinton defeated Barack Obama in Kentucky's primary in 2008, and her husband Bill Clinton was the last Democrat to carry the Bluegrass State in a general election.

On Sunday, playing up her husband's popularity, the former first lady appeared to indicate Bill would play a role in her administration if she were elected, promising to put him "in charge of revitalizing the economy." She later said she would not give him a cabinet position.

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