By John Whitesides

FLINT, Mich. (Reuters) - The Flint water crisis has united Democrats Hillary Clinton and Bernie Sanders in outrage, but some residents suffering through the city's major public health scandal want more than talking points from the presidential contenders.

As Flint becomes the focal point of the Michigan primary battle when it hosts a nationally televised debate on Sunday, residents want to see Clinton and Sanders push harder for funding to replace the city's crumbling water pipes, pay for long-term medical needs and lower their water bills.

"We don't want our pain to be exploited as a political backdrop. We need more from both of the candidates," said Nayyirah Shariff, a Flint resident and co-founder of the activist Flint Democracy Defense League who has met with both Clinton and Sanders.

The crisis in Flint, a predominantly black city of 100,000, was triggered when an emergency city manager installed by Governor Rick Snyder switched the city's water supply from Lake Michigan to the nearby Flint River to save money.

The change corroded Flint's aging pipes and released lead and other toxins into the water supply, exposing thousands of residents including children to high lead levels that have sparked serious health problems.

The crisis has sparked national outrage and led to calls for Snyder to resign.

Both Democratic presidential contenders have raced to condemn the water contamination and criticize Republican Snyder for a slow state response, linking it to broader racial and economic inequities.

But Melissa Mays, who has suffered seizures since the contamination and has three children with elevated lead levels in their blood, said she has not gone to local events where Clinton and Sanders met with residents.

"I'm not going to be used like that. I'm not going to be a token," said Mays, founder of Water You Fighting For?, another activist group. "Do something first, then I'll show up."

President Barack Obama declared a state of emergency in Flint in January, but lawmakers in Congress have been unable to agree on a funding package to replace aging pipes.

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DEBATE TO HIGHLIGHT CITY'S PLIGHT

The issue will get a full national airing from the Democratic presidential candidates in a debate in Flint scheduled to begin at 8 p.m. EST on Sunday.

Republican presidential candidates have steered clear of Flint on the campaign trail, but when U.S. Senator Marco Rubio was asked about Flint during Thursday's debate in Detroit he defended Snyder and said the "politicizing" of the crisis was unfair. The U.S. presidential election is in November.

Both Clinton and Sanders, who are vying for support from black voters in Michigan and nationally, have highlighted the crisis in Flint as an example of racial and economic inequality.

Clinton was quick to jump on the issue, sending aides to Flint to meet with local officials, visiting the city on Feb. 7 and pressing for adding the debate in Flint. She was rewarded with an endorsement from Flint Mayor Karen Weaver and several black pastors in the region.

Sanders also waded into the controversy, quickly calling for Snyder's resignation, but he did not visit Flint until Feb. 25, more than two weeks after Clinton.

Clinton gets credit from some residents for her aggressive approach, even if some see it as political expediency.

"She has certainly tried to bring a great deal of awareness to what has gone in Flint," said Rev. Allen Overton, a member of the Flint-area Concerned Pastors for Social Action group and a Clinton supporter. "Sanders is trying to catch up."

The Rev. Dan Scheid of St. Paul's Episcopal Church in Flint said the crisis raises questions about race and class - issues ripe for political exploitation.

"The cynic in me would say there is an understandable level of opportunism taking place," Scheid said. "But any attention the candidates can bring in putting this injustice in front of the country is helpful."

Keri Webber, whose entire family has been afflicted with an array of illnesses, including a daughter with lead in her bones, said she was frustrated by the parade of politicians expressing sympathy for Flint but taking few concrete steps to help.

"The Democrats are trying to build a name off us, and the Republicans couldn't tell you where Flint, Michigan, is," Webber said.

(Editing by Paul Thomasch and Matthew Lewis)