WASHINGTON — Bernie Sanders pushed for a trifecta of wins in Saturday’s Democratic presidential caucuses in Hawaii, Alaska and Washington state, hoping to stoke a spring comeback against the commanding front-runner, Hillary Clinton.

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.

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 percent of the remaining delegates from primaries and caucuses to have a majority of those delegates by June’s end.