HOPKINSVILLE (AFP) - Polls opened on Tuesday (May 17) in a Kentucky primary that could give Mrs Hillary Clinton a chance to bolster her almost insurmountable delegate lead over Democratic rival Bernie Sanders, who has vowed to slog on despite long odds.
Though Mrs Clinton holds a slim poll lead, Senator Sanders was gunning for victory in the Bluegrass State, building 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 United States region where many feel they have been given the cold shoulder in the lukewarm recovery from the 2007-2008 financial crisis.
The north-west state of Oregon on Tuesday was also holding its Democratic and Republican primaries, where limited polling has indicated Mrs Clinton is ahead.
Mrs Clinton sees Kentucky as an opportunity to appeal to working-class white men - a demographic where she has lagged both the presumptive Republican nominee Donald Trump and her Democratic rival Sanders.
Mr John Spenlau, 28, speaking to AFP on Tuesday outside a voting station in suburban Louisville, said he had voted for Sen Sanders.
"To be honest I don't think he's going to win the nomination but I prefer the idea of continued change," he said referring to Sen Sanders proposals to upend what he calls an unfair political and economic system in the US and fight 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," Mr Spenlau said.
No Democratic presidential candidate has won in Kentucky state since 1980 except for her husband Bill Clinton.
On Sunday, the former first lady appeared to indicate Mr Clinton would play a role in her administration if she were elected, promising to put him "in charge of revitalising the economy".
And during a stop on Monday at a diner in Paducah, a city in the state's south-west, she reasserted that he would be her ally in office.
"I've already told my husband that if I'm so fortunate enough to be president and he will be the first gentleman, I'll expect him to go to work... to get incomes rising."
Sen Sanders has also been investing time in Kentucky.
He was in Paducah on Sunday and Bowling Green Monday, holding much bigger rallies - each more than 2,000 people.
The Clintons have struggled to contain the damage from comments Hillary made in March, when she said she expected to "put a lot of coal companies and coal miners out of business".
She made the remark during a speech on renewable energy but the soundbite stung many in Appalachia.
In Fort Mitchell at the weekend she emphasized her determination to help coal country, saying: "We can't and we must not walk away from them."
Mrs Clinton made three stops in Kentucky on Sunday and another four Monday, shaking hands, taking selfies, offering hugs - and even chatting with Trump supporters who vowed never to vote for her.
With the Democratic nomination in sight, Mrs Clinton is repositioning herself for a bruising general election campaign battle against Mr Trump.
In a November face-off the billionaire appears destined to hold an advantage over Mrs Clinton, at least initially, with working-class whites.
At a rally in Hopkinsville, Kentucky's secretary of state and close Clinton friend Alison Lundergan Grimes made the case for a steady hand over Mr Trump's unpredictability and the Republican Party's reluctance to unite around their presumptive nominee.
"They have dysfunction. We have a candidate with a plan," Ms Grimes said.
Mrs Clinton used the rally to pummel the "risky and dangerous" Mr Trump, suggesting he is unqualified to handle tough foreign policy decisions.
She pointed to her work in late 2012 in helping to defuse sky-high tensions between Israelis and Palestinians, in part by negotiating at length with Egypt's then-president Mohamed Mursi.
"Now ask yourself: how hard would it be for America's secretary of state to negotiate with a Muslim leader if someone running for president - or heaven forbid were president - was spending a lot of his time denigrating the religion of the people we had to deal with in a flashpoint region?"