Democratic presidential candidates Hillary Clinton and Bernie Sanders battled for a single delegate Thursday in Kentucky, but a review of primary election results didn't change the outcome of the May 17 primary.

The review, held at the request of the Sanders' campaign, put Clinton in line to pick up an extra delegate from the Bluegrass state, while elsewhere, Donald Trump secured the Republican nomination for president.

If the Kentucky results stand, Clinton would need just 77 more delegates to secure the nomination. She leads Sanders by 271 pledged delegates and has a nearly 500 delegate advantage in superdelegates.

Fewer than 2,000 votes separate Clinton and Sanders in Kentucky, or less than one half of 1 percent of all votes cast in the state. Both candidates picked up 27 delegates from the state, but one delegate from the 6th Congressional District has not been awarded. Thursday's recanvassing -- a review of totals from electronic voting machines and absentee ballots -- confirmed Clinton leads Sanders by about 500 votes in the district. If the results hold, Clinton would win the extra delegate.

Sanders still has options. He could ask a judge to order a recount, which is a more thorough examination of the results. But Sanders would have to pay for that himself, a costly gamble given the reward would likely be just a single delegate. The deadline to ask for a recount is Friday.

Sanders won nearly every coal-producing county in Kentucky, underscoring Clinton's weakness in Appalachia after her comments that her policies would put a lot of coal miners and coal companies out of business. Clinton has said she was mistaken in her remarks and has since touted her plan to invest billions of dollars in economically depressed coal regions.

Clinton enjoyed the support of most of Kentucky's Democratic leaders, including former Gov. Steve Beshear and Secretary of State Alison Lundergan Grimes.