Sen. Bernie Sanders supporters fill the Moda Center in Portland on August 9 for a campaign rally. John Sepulvado / OPB

Bernie Sanders will make his first Oregon campaign stop of 2016 when he holds a Friday morning rally at Portland’s Moda Center.

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Sanders is appearing in Portland one day before the Democratic presidential caucus in neighboring Washington. Oregon’s primary will be on May 17, although mail ballots will go out around the end of April.

Doors for the Moda Center event will open at 9:45 a.m. Sanders packed the 19,000-seat basketball arena when he held a rally there last August, and thousands more listened in on loudspeakers outside.

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The Vermont senator's campaign is planning an even bigger rally for Friday evening in Seattle, where he will appear at Safeco Field. The Mariners play there and it has a capacity of nearly 48,000 for baseball. On Thursday, Sanders will hold a morning rally in Spokane and an evening event in Yakima.

Presidential hopeful Bernie Sanders spoke to a crowd of supporters outside of Hudson's Bay High School in Vancouver, Washington. It was one of three campaign stops the Vermont Senator had in Washington Sunday. Bryan M. Vance / OPB People waited in the rain for hours ahead of Bernie Sanders' campaign event in Vancouver, Washington. Bryan M. Vance / OPB People waited in line for hours ahead of Bernie Sanders' campaign event in Vancouver, Washington. Bryan M. Vance / OPB A supporter holds up a Bernie Sanders for president sign during a rally in Vancouver, Washington, Sunday, March 20, 2016. Bryan M. Vance / OPB With a 5,000 person limit on the gym at Hudson's Bay High School, thousands of people were stuck out in the rain. Bernie Sanders stopped off to address them before heading inside to speak to the larger crowd. Bryan M. Vance / OPB Bernie Sanders supporters came out in support of the presidential hopeful, despite the rain. Thousands of people lined up for hours ahead of his campaign stop in Vancouver, Washington, Sunday for a chance to hear the Vermont Senator speak. Bryan M. Vance / OPB A young Bernie Sanders fan sports gray hair and thick glasses in an impersonation of the Vermont senator at a rally in Vancouver Sunday, March 20, 2016. Bryan M. Vance / OPB Democratic presidential hopeful Sen. Bernie Sanders spoke to an enthusiastic crowd of supporters at Hudson's Bay High School in Vancouver, Washington, Sunday, March 20, 2016. Sanders touched on each of his hallmark campaign points: campaign finance reform, wall street taxes and making public colleges and universities free. Bryan M. Vance / OPB A Bernie Sanders supporter wears a "Bern Baby Bern" T-shirt. Bryan M. Vance / OPB Speaking on education in America, Bernie Sanders told the crowd of more than 5,000 people packed into the gym at Hudson's Bay High School that he will make public college and universities free if he is elected president. Bryan M. Vance / OPB Bernie Sanders received a chorus of cheers as he spoke about reforming taxes on Wall Street. The Vermont senator also criticized competitor Hillary Clinton's campaign for accepting money from people on Wall Street. Bryan M. Vance / OPB A young Bernie Sanders supporter holds a sign during a rally for the presidential hopeful at Hudson's Bay High School in Vancouver, Washington, Sunday, March 20, 2016. More than 5,000 people crammed into the high school's gym to hear Sanders speak. Bryan M. Vance / OPB A crowded gym listens attentively to Vermont Sen. Bernie Sanders' speech during a campaign rally in Vancouver, Washington, Sunday, March, 20, 2016. Bryan M. Vance / OPB 

Democratic front-runner Hillary Clinton has not yet been in Oregon this year. But

former President Bill Clinton made a brief appearance in Portland

on Monday while campaigning for his wife.

The Sanders campaign said that people planning to attend the Portland event should RSVP at his website.