Clinton's loss in economically struggling West Virginia signals trouble for her in other industrial states.
US Democratic White House candidate Hillary Clinton lost a nominating contest to Bernie Sanders in economically struggling West Virginia on Tuesday, a setback that could signal trouble for her in industrial states in the November general election.
The defeat slows Clinton's march to the nomination, but she is still heavily favoured to become the Democratic candidate in the Nov. 8 election.
Still, her failure to win over voters deeply skeptical about the direction of the economy underscored the work she will need to do to court working-class voters in the Rust Belt, which includes key states such as Ohio and Pennsylvania. West Virginia has one of the highest unemployment rates in country.
Sanders, who has vowed to take his campaign all the way to the Democrats' July 25-28 convention in Philadelphia, said he is the stronger candidate to beat presumptive Republican nominee Donald Trump in November.
"Working people are hurting," Sanders said in Oregon on Tuesday night after his West Virginia win. "We need an economy that works for all of us, not just the one percent."
Trump, 69, won contests in West Virginia and Nebraska handily on Tuesday. Trump is set to meet with party leaders in the US Congress on Thursday, including US House of Representatives Speaker Paul Ryan.
After Ryan said last week that he was not yet ready to endorse Trump, Trump said on Sunday that he would have to decide whether he still wanted Ryan to preside over the party's July convention.
Trump said on Tuesday night that he would like Ryan to chair the convention as planned. "He's a very good man, he wants what's good for the party," the New York billionaire said.
Trump has zeroed in on Clinton's protracted battle with Sanders, a 74-year-old U.S. senator from Vermont. He has taunted Clinton in recent days by saying she "can't close the deal" by beating Sanders, her only rival for the Democratic Party's nomination since Feb. 1.
Clinton, 68, has said she will ignore Trump's personal insults, including his repeated use of his new nickname for her, "Crooked Hillary," and instead will criticise his policy pronouncements.
In West Virginia, roughly six in 10 voters said they were very worried about the direction of the US economy in the next few years, according to a preliminary ABC News exit poll. The same proportion cited the economy and jobs as their most important voting issue.
A remark Clinton made at an Ohio town hall in March that the country would "put a lot of coal miners and coal companies out of business" may have hurt her with voters in coal-mining states such as West Virginia.
During Clinton's visit to West Virginia and Ohio last week she repeatedly apologised to displaced coal and steel workers for her comment, which she said had been taken out of context, and discussed her plan to help retrain coal workers for clean energy jobs.
To secure the Democratic nomination, a candidate needs 2,383 delegates. Going into West Virginia, Clinton, a former US secretary of state, had 2,228 delegates, including 523 so-called superdelegates, elite party members who are free to support any candidate. Sanders had 1,454 delegates, including 39 superdelegates. Another 29 delegates will be apportioned based on West Virginia's results.
Clinton and Sanders will compete in another primary contest on May 17. Both candidates are also looking ahead to the June 7 contests, the last in the long nominating season, in which nearly 700 delegates are at stake, including 475 in California, where Sanders is now focusing his efforts.
Trump, shifting into general election mode, has already begun to consider running mates. He said on Tuesday night that he has narrowed his list to five people.