Democrats in Congress dealt a blow to President Obama's agenda last week when they blocked a bill to fast-track the Trans-Pacific Partnership (TPP), a massive free-trade deal with Asia he has been negotiating.

But that victory isn't enough for Sen. Bernie Sanders, the independent senator from Vermont who is running for the Democratic nomination. He also wants his fellow Democratic candidate, former Secretary of State Hillary Clinton, to join the coalition of lawmakers who disagree with the president on trade.

"Corporate America and Wall Street are going to bring that bill back to the House next week. I would hope very much that Secretary Clinton will side with every union in this country, virtually every environmental group, many religious groups, and say that this TPP policy is a disaster, that it must be defeated, and that we need to regroup and come up with a trade policy which demands that corporate America start investing in this country rather than in countries all over the world. So I look forward to working with the secretary on this issue," Sanders said Sunday on CBS' "Face the Nation."

In a separate interview, Clinton campaign manager Robby Mook rejected the suggestion that his boss has been on the sidelines of the trade issue.

"There will be no tougher fighter at the negotiating table for every day Americans when these trade agreements are being negotiated, so families can trust her to fight hard for them in any of these agreements but Hillary has been abundantly clear about where she stands on the issue of trade," Mook said.

He said Clinton has laid out three key principles for any trade agreement: It must protect American jobs, increase wages for American workers and be consistent with U.S. national security interests.

But since declaring her candidacy for the Democratic nomination, Clinton hasn't said whether she supports TPP or the legislation that would fast-track the trade deal through Congress by requiring lawmakers to vote yes or no on the deal without amending it. She spoke favorably of TPP in her 2014 memoir, "Hard Choices."

Mook argued that it's not a problem that Clinton hasn't taken a stance since the administration hasn't made the text of the TPP deal public, and called the current dispute between Congress and the administration "about procedures and parliamentary this and that."

"You can't take a position on a trade bill that you can't see, and so Hillary's trying to be responsible and wait until we have something to react to, but she has a very clear set of tests that any trade bill will need to meet," he said.

Though Sanders seemed to argue the same point - saying it's "a little bit silly" for members of Congress to be voting on a trade deal they haven't seen yet - he also said that past trade deals have taught him enough about how free trade deals play out in America.

"There is no question in my mind, and I think the minds of most Americans, that what our trade policy has been for many years is to allow corporate America to shut down plants in this country, move abroad, hire people at pennies an hour, and then bring their products back into the United States," Sanders said. "It is a failed trade policy, and I would hope that the secretary joins [Massachusetts Sen.] Elizabeth Warren, [Ohio Sen.] Sherrod Brown, and the vast majority of Democrats in the Congress in saying, 'No, we've got to defeat this piece of legislation.'"

Sanders has resisted criticizing Clinton but is getting more vocal about issues on which he believes the former secretary of state has gone wrong. Aside from trade, he pointed to three issues where he believes he has a distinction: Clinton's vote in favor of the Iraq War versus his vote against it; his efforts to defeat the Keystone XL pipeline in Congress versus her relative silence on the issue; and his vote against the USA Patriot Act versus Clinton's vote in favor.

Plus, Sanders said, "I think the bottom line is the American people want leadership to take on the billionaire class, represent the middle class. I have been doing that for the last 25 years. People will have to judge the secretary's role in that process."

One other area where he stands out from other candidates is in his focus on small contributions rather than large checks for his campaign and a super PAC (he doesn't have one). He said that he has received donations from 200,000 people.

"I worry about us moving to an oligarchy, where our political system is controlled by the rich and the powerful. I am raising money from small, individual contributions," he said. "I don't want the money from the billionaires. And that's the way we're going to run our campaign."

Clinton, for her part, held her first large rally to kick off her campaign Saturday even though she declared her candidacy in April. Mook said the past two months were about "being accessible to everyday Americans" and "workshopping her policies."

"What you saw in her speech yesterday was the result of two months of hitting the ground, talking to everyday Americans, getting their input so that she could reflect what they want to see in their next president, and offer and get reaction to what she believes we need to be doing," he said.

But he denied that Clinton has a problem with credibility, even though a CBS News poll from late March showed that just 42 percent of American adults said Clinton was honest and trustworthy, while 47 percent said she wasn't.

"No poll says that," Mook said when asked about surveys that show Americans think Clinton has a deficit of trustworthiness. "But first of all, the central question in this race is whether voters can trust Hillary Clinton to be a tenacious fighter for them, to go to bat for them, to push back on the stacked deck that has kept the middle class behind. And the answer to that is overwhelmingly yes."