Bernie Sanders will try to claw back Hillary Clinton's lead in the race for the Democratic nomination for the US presidency on Saturday in caucus votes in Washington state, Hawaii and Alaska.
Mr Sanders remains a dogged pursuer but Mrs Clinton has 1,691 of the 2,383 delegates needed to win, AP reports.
He is still attracting tens of thousands to his rallies, on Friday calling for a "political revolution".
Mrs Clinton pointed out she has "2.6 million more votes" than Mr Sanders.
Saturday's voting is just for the Democratic nomination.
Bigger battles ahead
Mr Sanders has spent the week on the west coast, rallying support among liberals and the left-wing.
Late on Friday in Seattle's Safeco baseball stadium, he repeated key elements of his policy platform, urging economic equality and universal health care.
He said: "Real change historically always takes place from the bottom on up when millions of people come together. We need a political revolution!"
However, he also suffered defeat in Arizona, and although his delegate haul from the three states was 20 higher than Mrs Clinton, he has failed to make major inroads into her lead.
Mrs Clinton has also been campaigning in Washington state. She told supporters in Everett: "We are on the path to the nomination, and I want Washington to be part of how we get there."
She also focused on this week's deadly attacks in Brussels, condemning Republican rivals Donald Trump and Ted Cruz for their "reckless" foreign policies.
Opinion polls are scarce and tricky in caucus elections - a series of meetings in which voters give their support for candidates with an open show of hands.
However, Mr Sanders has used his appeal with grassroots activists to benefit from the voting system in the past. He has done particularly well among young voters.
Washington is the biggest prize, with 101 pledged delegates available. Hawaii has 25 delegates at stake and Alaska 16.
Whatever happens on Saturday, the battle will be won and lost in far bigger states still to come. In RealClearPolitics poll averages, Mrs Clinton has the lead over Mr Sanders by nine percentage points in California, 34 points in New York and 28 in Pennsylvania.
Calculations suggest Mr Sanders may need to win two-thirds of the remaining delegates - in primaries, caucuses and among so-far uncommitted super-delegates - the unelected officials who can vote for their candidate of choice at the party's election convention.