"The game is rigged, and the Republicans rigged it," Warren said to loud cheers.
It's part of a three-state tour of Senate campaigns for Warren, who later Saturday headed to St. Paul for a get-out-the-vote rally on behalf of Franken, Gov. Mark Dayton (D) and other candidates. Franken and Dayton are strong favorites to win reelection next month.
On Friday Warren stopped in the Denver suburbs to help Sen. Mark Udall (D-Colo.) in his tough reelection campaign. And on Sunday, Warren will be on the stump in Iowa for Rep. Bruce Braley (D), who is in a neck-and-neck race for the seat of retiring Sen. Tom Harkin (D-Iowa). It's Warren's first visit in this election season to the battleground state, home to the first-in-the-nation caucus in early 2016 for the presidential campaign.
The crowd at Carleton -- where Wellstone served as a professor before launching his long-shot 1990 Senate bid -- gave its loudest cheers to Warren, whose fights against big banks have made her a hero to liberal activists.
"She's amazing. She shows that politics is a good thing," said Rachel Palermo, 21, a senior at neighboring St. Olaf College. Some of her friends said they attended the rally just to see Warren.
Palermo and her friends said they want Warren to run for president, but Alyssa Berg, 21, also a St. Olaf senior, noted it would be "counterproductive" for Warren to run against Hillary Rodham Clinton.
They settled on them running together as a ticket -- it's uncertain whether they prefer Warren or Clinton atop such a ticket.
Warren has declined past overtures at challenging Clinton in 2016, and she made no mention of any national ambition, but the crowd reaction cemented the impression that she is atop the list of sought-after speakers to energize liberal voters.
"She's a rock star," Franken told reporters afterward, declining to comment on whether she should consider national campaign.
In the audience was David Wellstone, the oldest son of the late senator. He hugged Franken -- a longtime family friend -- and Warren afterward, as she worked the rope line and was mobbed by adoring fans posing for cell-phone pictures with her.
Republicans have attacked Warren's anti-corporate positions as out of touch with small business. The campaign of Mike McFadden, Franken's Republican opponent, issued a statement blasting Warren and Franken for both voting with President Obama's positions 97 percent of the time.
In her more than 20-minute stump speech, Warren recalled her late-night conversations as a Harvard law professor with Wellstone in the late 1990s as he fought bankruptcy legislation supported by Wall Street.
Pumping her fists in the air, waving to the crowd in the rafters of the hall, Warren delivered a speech that was a mix of professorial lecture and progressive call to arms.
She talked about her legislation, co-sponsored by Franken, that would allow borrowers to refinance their education loans, an issue that drew huge applause on a campus where tuition, room and board is close to $60,000. Banks have fought the bill, which was filibustered by Republicans in the Senate, and Warren pledged to take the fight against banks on the issue early next year.
"We're coming after them," she said.