Clinton's rival Bernie Sanders is 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.
The two states are linked to coal, as is much of Appalachia, the largely white, long-struggling eastern US region where many feel they have been given the cold shoulder in the lukewarm recovery from the 2007-2008 financial crisis.
The state has been treated by Clinton as an opportunity to appeal to a demographic that has consistently snubbed her: working-class white men.
No Democratic presidential candidate has won Kentucky since 1980 except Bill Clinton.
On Sunday the former first lady appeared to indicate that her husband would play a role in her administration if she were elected, promising to put him "in charge of revitalizing the economy."
Asked during a stop yesterday at a diner in Paducah, a city in southwestern Kentucky, whether Bill would be part of her cabinet, she shook her head and said "No" - but 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."
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 comment during a speech on renewable energies, but the soundbite stung many in Appalachia.