Hillary Clinton eked out a photo finish win in Kentucky’s primary, but her Democratic White House rival Bernie Sanders claimed a solid victory in Oregon.
With 99% of ballots counted, Mrs Clinton had a lead in the Bluegrass state of 46.7% to 46.3% – just 1,813 votes.
But Mr Sanders was projected the winner of Oregon’s primary on Tuesday, by 53% to 47%.
The Vermont senator has built on his commanding victory last week in neighbouring West Virginia.
But Mrs Clinton, a former Secretary of State, remains on track to clinch the Democratic presidential nomination in early June.
Mr Sanders has vowed to continue fighting until July’s party convention, a distraction for his rival’s campaign.
The Clinton camp is eager to focus on presumptive Republican nominee Donald Trump ahead of November’s election.
Mr Trump won Oregon’s primary by 64.2% on Tuesday, a victory which was a foregone conclusion since he is now running unopposed.
Mrs Clinton easily beat her then-Democratic rival, Barack Obama, in Kentucky’s primary in 2008.
Her husband, Bill Clinton, was the last Democrat to carry the state in a general election.
Tuesday’s contests took place amid an ugly dispute among the Democrats following chaotic scenes at the party’s Nevada convention on Saturday.
Sanders supporters threw chairs, heckled speakers and harassed the state party chair with death threats.
They accused the party leadership of rigging the results of the convention to award more delegates to Mrs Clinton, who won the state’s caucuses in February.
Heading into Tuesday, Mrs Clinton had the backing of 2,240 delegates, including 524 so-called super delegates who can change their allegiance at any time before the party’s convention.
Mr Trump stoked controversy on Tuesday when he said in an interview with Reuters news agency he would be willing to talk to North Korean leader Kim Jong-un.
Melania Trump, meanwhile, spoke up for her husband in an interview with DuJour magazine, saying: “He’s not Hitler. He wants to help America.”