"Well, he doesn’t dress particularly well," Sanders said about himself. "He’s an interesting guy, but obviously not a serious candidate. Imagine standing up for working people and taking on the billionaire class. What a laughable idea that is. Who’s going to support that idea?"

The crowd of nurses erupted in applause and shouts of "We will!"

Sanders noted a steady climb in turnout to his rallies, bumping from 5,000 in Denver in June to a 28,000-person record Sunday night in Portland.

NNU Executive Director RoseAnn DeMoro said Sanders is a legislator -- "I don't call Bernie a politician" -- who aligns perfectly the union across the board. She mentioned protections for nurses and patients from Ebola, Sanders' introduction of a Wall Street "speculation tax" and his support of a single-payer health care system.

The union noted that Sanders' policy points "align with nurses from top to bottom."

One issue likely to play out as both Clinton and Sanders court major unions will be the Trans-Pacific Partnership -- a President Barrak Obama's trade deal involving a dozen countries. The American Federation of Labor and Congress of Industrial Organizations has serious concerns about the deal, and both candidates are courting the powerful national labor federation.

Sanders said he would "lead the effort to prevent the passage of the TPP," and that several of the proposed member countries are fighting back over a provision of the deal that would "extend the copyright for prescription drugs, preventing poor countries from getting generics." Details of the proposal have not been made public.

Rallies on the west coast haven't been all love for the Vermont senator. He took some heat Saturday in Seattle from people identifying with the Black Lives Matter movement. Since then, his campaign released a racial justice policy platform and hired a new national press secretary.

"I see the issue for racial justice in two directions," Sanders said in Oakland Monday. "Number one, to end every vestige of institutional racism in this country and reform criminal justice, but equally important, to make sure that we have an economy where kids today who are born in poverty can in fact make it into the middle class and can get the education and the jobs they need."

Asked about another populist presidential candidate on a meteoric rise, Sanders didn't have much to say. He spent only nine words on Republican front runner Donald Trump.

"I'll let his mother explain Donald Trump," he said. "I can't."