OLYMPIA, Wash. (AP) — Former Vice President Joe Biden took the lead over Vermont Sen. Bernie Sanders in Washington after additional results in the vote-by-mail state posted Wednesday afternoon.

Biden led by about 15,000 votes after more than 1.6 million votes were counted. Results could continue to change as ballots dropped in drop boxes Tuesday or those which may still be in the mail arrive at elections offices and are processed. Counties will update their results again Thursday afternoon.

Of the state’s 89 pledged delegates, only 31 are allocated based on the statewide result. The remaining 58 are determined based on the results of the state’s 10 congressional districts, and those results might not be calculated until the election is certified by the secretary of state’s office, which could be as late as March 27.

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Democrats are using the vote-by-mail presidential primary — moved up this year from May — for the first time to allocate delegates instead of the smaller caucuses used in previous years.

The Washington ballot had 13 candidates on it, along with an ‘uncommitted’ option. But it was essentially a two-person race between former Vice President Joe Biden and Vermont Sen. Bernie Sanders. President Donald Trump was the only candidate listed for Republicans. Trump received more than 550,000 votes, and more than 8,500 Republican wrote in an alternate candidate. More than 356,000 Democrats voted for candidates other than Biden or Sanders.

In 2016, Sanders won more than two-thirds of the delegates from the Washington caucuses that year, which were attended by about 230,000 Democrats. More than 800,000 Democrats sent in ballots for the primary later that year — which Hillary Clinton won — even though their vote didn’t count for the nominating process.

The state Democratic Party’s central committee voted last year to start using a hybrid system that uses the state’s vote-by-mail system for a presidential primary to apportion delegates to candidates, and caucuses and conventions to select which delegates will represent the state at the national convention in Milwaukee in July. Also last year, Washington Gov. Jay Inslee signed a measure moving the state’s presidential primary from May to the second Tuesday in March.

Will Casey, a spokesman for the state Democrats, said that under Democratic National Committee Rules, if any listed candidate hits the 15 percent threshold in voting, they are allotted delegates, even if no longer in the race. Those delegates will be pledged to that candidate on the first ballot, though they can ultimately be released by that candidate. As of Wednesday night, no one other than Biden and Sanders surpassed the 15 percent threshold.