Whitmer countered that El-Sayed, who refuses corporate political action committee donations, had accepted at least $170,000 in individual donations from business executives.
"You can't be half-pregnant on this one," she said, adding that she has the "real grassroots campaign."
Whitmer, a former legislative leader, and El-Sayed, Detroit's ex-health director, are running in the Aug. 7 primary that also includes wealthy entrepreneur Shri Thanedar. He avoided going negative in a debate that included sharp exchanges between his opponents.
El-Sayed said Whitmer takes credit for helping to expand Medicaid but also accepts money from corporations and individuals "who want to maintain the status quo." He called for a state-level single-payer health care system to cover all residents.
Whitmer countered that she wasn't "going to be lectured by anyone on this stage or even on the other side of ballot on health care." She said she battled an insurance company that was wrongfully denying her mother chemotherapy for a deadly brain tumor, and helped expand Medicaid to 680,000 additional people.
El-Sayed said he appreciated Whitmer's role with the Medicaid expansion but criticized a closed-door fundraiser that Blue Cross Blue Shield of Michigan's PAC held for her campaign.
"We don't what was said. We don't know what kind of deals were cut. That's the kind of corporate corruption we cannot sustain in our health system in Michigan," he said.
He also brought attention to Build a Better Michigan, a nonprofit organized by Whitmer allies to launch a $1.8 million TV ad campaign on her behalf. He contended it is a means to put "unlimited amounts of corporate money into our politics to move a message," and the public does not yet know the donors.
The group has said it disclosed its donors in a report mailed by a deadline that was earlier this week, but it will not make it public until the Internal Revenue Service accepts it.
"Give me a break, Abdul," Whitmer said while citing his campaign's contributions from corporate executives. "My organization, my campaign is playing by the rules."
The winner of the Democratic primary will face one of four Republicans in the November election: Attorney General Bill Schuette, Lt. Gov. Brian Calley, state Sen. Patrick Colbeck or Dr. Jim Hines.
The Democrats answered questions about business taxes, tax increases, tariffs, marijuana legalization, road conditions and other topics during the hour-long debate hosted by WDIV-TV in Detroit and the Michigan Democratic Party.
Thanedar, who has owned chemical-testing companies and has given his campaign nearly $6 million, said he is the only gubernatorial candidate who has created jobs and contended that he is best-positioned as a contrast to GOP front-runner Bill Schuette.
"I will make Michigan inclusive and progressive," he said.