WASHINGTON — Hillary Clinton was clinging to a razor-thin lead on Tuesday over rival Bernie Sanders in Kentucky, where a win would blunt his momentum and help her move closer toward clinching the Democratic presidential nomination.

Clinton has a commanding lead in the all-important national delegate count and is marching toward vying for the presidency in the November 8 general election despite a string of recent primary losses.

Victories in Kentucky and Oregon, the other state voting on Tuesday, would halt her slide and help reverse the narrative that her campaign is showing significant weakness ahead of an almost certain showdown between Clinton and Donald Trump, the Republican Party’s presumptive nominee.

But more than three hours after polls closed, the race remained too close to call. With 99 per cent of precincts reporting, Clinton led Sanders by 46.7 per cent to 46.3 per cent – a margin of less than 2,000 votes.

Polls in Oregon, which holds Democratic and Republican primaries, close at 8:00 pm (0300 GMT Wednesday). Limited polling there showed Clinton ahead on the Democratic side.

Sanders had counted on a Kentucky victory to build on his win last week in neighboring West Virginia as he battles to keep his long-shot nomination bid alive.

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.

"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.

Kentucky held its Republican caucus in March.

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 programmes that I believe in," Spenlau said.

’Risky and dangerous’

Clinton, 68, made three stops in Kentucky on Sunday and four more Monday, shaking hands, taking selfies, offering hugs – even chatting with Trump supporters at a smoke-filled diner in the southwestern city of Paducah.

"I will not vote for you. I will never vote for you," disabled veteran Dianna Dooley, 66, told her.

Clinton kept her composure, saying: "That’s OK. You vote for whoever you want." Sanders, 74, invested time in Kentucky as well, campaigning in Paducah on Sunday and Bowling Green on Monday.

But with the Democratic nomination in sight, Clinton is looking beyond the showdown with Sanders to position herself for a bruising campaign battle against Trump.

At a rally in Hopkinsville, Clinton pummeled the "risky and dangerous" Trump, suggesting he is unqualified to handle tough foreign policy decisions.

A main "super PAC" supporting Clinton on Monday unveiled a new television ad that skewers Trump for his treatment of women.

The ad, which will air across the crucial swing states of Ohio, Florida, Virginia and Nevada, shows women mouthing Trump’s own words, including "you could see there was blood coming out of her wherever," a comment Trump made last year in reference to a debate moderator who asked him tough questions.

Trump shot back on Tuesday with criticism that could foreshadow the tone of the coming election battle.

"Amazing that Crooked Hillary can do a hit ad on me concerning women when her husband was the WORST abuser of woman in US political history," Trump tweeted. — AFP