“I’ve known Hillary Clinton for 25 years and I have a lot of respect for her,” Sanders said, but emphasized the differences between the two presidential hopefuls on several issues, including the Trans-Pacific Partnership.

“I frankly don’t understand how you could be a major candidate for president of the United States — Hillary Clinton, or anybody else — and not have an opinion on that issue,” he said.

Clinton has outlined a few general principles for what the TPP ought to accomplish, but has declined to say explicitly whether she thinks the trade pact has actually met those conditions.

Asked whether he thought her silence is a “cop-out,” Sanders replied, that, “Yes. It is.”

The self-described socialist from Vermont has fared well so far with his fundraising despite lacking major corporate backers. Sanders’ presidential campaign raised more than $1.5 million in its first 24 hours, with the average donation hovering around $40. In total, Sanders said, he has already raised $6 million from 150,000 supporters – and predicted that number would rise to $10 million by the end of June.

“This is not an educational campaign. This is not a protest campaign. This is a campaign to win,” Sanders said Thursday, telling reporters that his campaign would be unveiling a comprehensive tax plan, which would tax Wall Street speculation and end loopholes that allow corporations to take advantage of overseas tax havens.

The proposal, as POLITICO reported, would also include an increase on taxes for wealthy Americans to pay for health-care and education investments and would likely raise marginal tax rates above 50 percent.