Michigan Gov. Rick Snyder is accusing Democrats of turning the city of Flint's toxic water crisis into a political football -- as they line up to lambaste the Republican governor while saying little about the role of a former Democratic mayor or federal agencies in the public health emergency. 

Presidential candidates Hillary Clinton and Bernie Sanders were the latest to go after Snyder. During Sunday night's debate, Clinton claimed Snyder didn’t appear to care about the lead that has contaminated Flint’s drinking water.

"We've had a city in the United States of America, where the population, which is poor in many ways, and majority African-American, has been drinking and bathing in lead-contaminated water," Clinton said. "And the governor of that state acted as though he didn't really care. He had requests for help that he basically stonewalled."

Sanders called on Snyder to simply resign. 

Meanwhile, Flint Mayor Karen Weaver, a Democrat, visited the White House on Tuesday to address the issue. 

And President Obama is expected to assign a "tsar" to oversee the crisis, Fox News has learned.

Weaver is meeting with Valerie Jarrett, a top aide to the president, and purportedly will try to talk on Capitol Hill with Michigan's two senators, then get home in time for Snyder's state of the state address.  

Snyder, who has faced similar accusations from liberal activists, responded by saying in a tweet that “political statements and finger pointing” are not helping. 

There is little question that the state bears significant responsibility for the public health crisis. Snyder apologized in December and Michigan's top environmental regulator, Dan Wyant, resigned after a task force created by Snyder blamed problems on his agency. 

The group said the Department of Environmental Quality erred by not requiring Flint to keep corrosive water from leaching lead from service pipes into residents' homes and belittling concerns from the public. The city had switched from Detroit's water system to Flint River water in a cost-cutting move in 2014, while under state financial management. 

Residents complained about the water's taste, smell and appearance, and children were found to have elevated levels of lead due to the water supply; lead exposure can cause behavior problems and learning disabilities in children.

The city returned to Detroit water in October.

However, the attacks on Snyder omit any mention of former Democratic Flint Mayor Dayne Walling or the federal Environmental Protection Agency.

The EPA’s top Midwest official told The Detroit News the agency knew about the lack of corrosion control in the water supply as early as April, after an EPA official identified problems with the drinking water, but did not make the information public.

The paper also cited email exchanges between EPA officials and Walling showing what it described as a “lack of urgency” over the matter and a greater focus on procedure rather than public safety. Walling and other officials repeatedly told residents the water was safe but blamed state and federal agencies for the problems.

Walling was voted out in November, with the water issue cited as a reason for his loss. Neither Walling nor the EPA’s alleged role in the crisis appeared in any criticisms from either Clinton or Sanders. 

The EPA has not responded to a request for comment. 

President Obama, meanwhile, designated Flint a federal emergency on Saturday but has refused Snyder’s request to designate it a disaster zone as it is a man-made incident.

Left-wing activist Michael Moore, who has famously advocated for his hometown of Flint in his documentaries, praised Clinton on Twitter for calling out Snyder.

Moore later sent out a tweet calling Snyder a criminal.

Moore isn’t the only liberal activist to blast the situation as criminal. Rev. Jesse Jackson told a crowd Sunday that there should be "tape around the city, because Flint is a crime scene." 

Fox News' Chad Pergram and The Associated Press contributed to this report.