WASHINGTON >> Bernie Sanders won Democratic presidential caucuses in Alaska and Washington state on Saturday, victories he hopes will stoke a spring comeback against the commanding front-runner, Hillary Clinton.

The Vermont senator was trying to build his enduring support among liberal activists into a three-state sweep that could help him narrow a gap of 300 delegates won in primaries by Clinton. The two Democrats were also competing in Hawaii.

While Sanders faces a steep climb to the nomination, a string of losses for Clinton would highlight persistent vulnerabilities within her own party. Sanders continues to attract tens of thousands to his rallies — drawing more than 17,000 in Seattle this week — and has collected more than $140 million from 2 million donors.

Speaking at a campaign rally in Madison, Wisconsin, before voters in Hawaii gathered for their caucuses, Sanders cast his wins Saturday as part of a Western comeback, citing recent victories in Utah and Idaho as a sign that his campaign still had a path to the nomination.

“We just won the state of Washington. That is what momentum is about,” he said. “Don’t let anybody tell you we can’t win the nomination or we can’t win the general election. We’re going to do both of those things.”

Most of his dozen primary-season wins have been in states with largely white populations and in caucus contests, which tend to attract the most active liberal Democrats. He’s heavily favored by younger voters, who were a key part of the coalition that boosted Obama to victory twice.

In Spokane, Washington, a huge line of caucus attendees snaked around a high school parking lot on Saturday morning.

“I think one of the biggest things is free tuition for students,” said Savannah Dills, 24, a college student who supports Sanders. “And getting big money out of politics. He’s not paid for by billionaires.”

Retiree Dan McLay, 64, attended the caucus in a hard-hat, which he joked he needed because he was one of the relatively few Clinton supporters in the big crowd.

“Look at this thing in Brussels,” McLay said, referring to the deadly bombings. “We need a real experienced leader.”

For Sanders, turning passionate support into the party nomination has grown increasingly difficult.

Clinton had a delegate lead of 1,223 to 920 over Sanders going into Saturday’s contests, according to an Associated Press analysis, an advantage that expanded to 1,692-949 once the superdelegates, or party officials who can back either candidate, were included.

Based on that count, Sanders still needs to win 58 percent of the remaining delegates from primaries and caucuses to have a majority of those delegates by June’s end.

His bar is even higher when the party officials are considered. He needs to win more than 67 percent of the remaining delegates overall — from primaries, caucuses and the ranks of uncommitted superdelegates — to prevail.

Because Democrats allocate their delegates on a proportional basis, meaning that the popular vote loser can still pick up a share, his Saturday victories netted Sanders a gain of at least 27 delegates to at least five for Clinton.

Sanders spent several days campaigning in Washington state and dispatched his wife, Jane, to Alaska and Hawaii. Clinton campaigned in Washington state for one-day and did not send any high-profile supporters to either of the other two states.

Clinton has been looking past the primary contests and aiming at potential Republican challengers. In interviews, rallies and speeches this week, she largely focused on Tuesday’s deadly attacks in Brussels, casting GOP front-runner Donald Trump and Texas Sen. Ted Cruz as unqualified to deal with complicated international threats.

Her campaign sees the April 19 contest in New York as an important one, not just because of the rich delegate prize but because losing to Sanders in a state she represented in the Senate would be a psychological blow. She hopes to lock up an even larger share of delegates in five Northeastern contests a week later.