The Vermont senator spent much of the week on the West Coast, trying to build his enduring support among liberal activists into a Saturday sweep that could help him narrow a gap of 300 delegates won in primaries behind Clinton. That’s about double the margin that then-Illinois Sen. Barack Obama held over Clinton in the 2008 primaries.

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.

Bernie Sanders Outraised Clinton in February

But turning that passionate support into the party nomination is growing increasingly difficult. Clinton has a delegate lead of 1,223 to 920 over Sanders, according to an Associated Press analysis, an advantage that expands to 1,691-949 once the superdelegates, or party officials who can back either candidate, are included.

Based on that count, Sanders still needs to win 58% 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% of the remaining delegates overall—from primaries, caucuses and the ranks of uncommitted superdelegates—to prevail.

“I have gotten 2.6 million more votes than Bernie Sanders,” Clinton told supporters crowded into a union hall in Everett, Washington, this week. “We are on the path to the nomination, and I want Washington to be part of how we get there.”

Sanders implored thousands of supporters in Spokane to come see him speak again Saturday—at a caucus. “Get there early,” he said. “Let’s have a record-breaking turnout.”

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On Tuesday, Sanders won caucuses in Utah and Idaho but lost Arizona—the largest delegate prize—to Clinton. Because Democrats allocate their delegates on a proportional basis, meaning that the popular vote loser can still pick up a share, those victories netted Sanders a gain of about 20 delegates.

He hopes to avoid a repeat of that performance by pulling out a win in Washington, which awards more than double the number of delegates than Hawaii and Alaska combined. He’s also looking to contests that follow in Wisconsin on April 5 and Wyoming on April 9 as a way to build momentum.

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.

Sanders dispatched his wife, Jane, to Alaska and Hawaii. Clinton, who held a conference call with supporters in Hawaii, did not send any high-profile supporters to campaign on her behalf.

Both candidates held several events in Washington state earlier this week.

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.

This article was originally published on Time.com