The Flint water crisis became an issue in the presidential campaign over the weekend, but it's been a slowly unfolding nightmare for the residents of the impoverished Michigan city for nearly two years.
Here is a timeline of key events — a road map of poor decisions, missed opportunities and broken promises — from the moment Flint agreed in 2013 to switch its water supply to Gov. Rick Snyder admitting this week that the mess could turn out to be his Hurricane Katrina.
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April 16: Flint inks an agreement to stop by water from Detroit and join a new water authority that will get water from Lake Huron, a deal that is expected to save the city millions. Although it will be three years before the new water source is available, Detroit says it will stop selling water to Flint in a year.
April 25: The city begins using water from the Flint River as a stopgap until the pipeline from Lake Huron can be completed. As officials raise glasses of water in celebration, Mayor Dayne Walling hails it as a "historic moment." He says "the water quality speaks for itself," and the state Department of Environmental Quality says residents shouldn't notice any difference.
May: Complaints about the new water start coming in. "It's just weird," resident Bethany Hazard tells the Flint Journal, referring to the murky, foamy quality of the H2O coming from her taps. The state DEQ says analysis of the water shows it meets state standards.
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June 12: City officials reveal they are treating the water with lime in response to complaints, but the mayor pooh-poohs concerns about safety. "I think people are wasting their precious money buying bottled water," he tells the Flint Journal.
Aug. 15: A boil advisory for part of the city is issued after water tests positive for e.coli bacteria. A second advisory will be issued just weeks later.
Oct. 13: After the General Motors plant in Flint refuses to use the river water because it's rusting car parts, the city arranges for the company to tap into a different water line. The residents of Flint still have to drink the river water.
Jan. 4: The city announces that Flint's water contains such a high level of trihalomethanes -- a disinfectant byproduct -- that it's in violation of the Safe Drinking Water Act. Officials say residents with normal immune systems have nothing to worry about. "Is water from the Flint River safe to drink? Yes," a city website declares.
Jan. 13: Protesters rally outside City Hall to demand a return to Detroit's supply and lower bills. Hundreds turn out at a forum, some complaining of rashes on children. Detroit offered to let Flint switch back, but the city's emergency manager says it would cost too much.
Feb. 18: A consultant hired by the city for $40,000 to investigate the water quality says it contains sediment and is discolored but is safe to drink.
Feb. 26: A manager at the U.S. Environmental Protection Agency tells Michigan officials that the chemistry of the river water means contaminants from pipes, including lead, are leaching into the water system.
April 2: As the city is forced to tell customers that it has flunked the Safe Drinking Water Act again because of the disinfectants, Mayor Walling posts a tweet: "(My) family and I drink and use the Flint water everyday, at home, work, and schools."
June 5: Activists file suit in attempt to stop the city from using river water. The city gets it moved to federal court, where a judge denies a preliminary injunction.
June 24: EPA water expert Miguel del Toral sends internal memo to his bosses flagging Flint's failure to use chemicals to control corrosion, which can cause lead to leach from pipes into drinking water. The warning was not made public until the ACLU leaked a copy of the memo weeks later.
July 22: Gov. Rick Snyder's chief of staff says in an email to the state Health Department that he believes the Flint residents are "concerned and rightfully so" about lead in the water. "These folks are scared and worried about the health impacts and they are basically getting blown off by us (as a state we're just not sympathizing with their plight)," he says. The agency says the data shows no increase in lead poisoning.
July 28: An epidemiologist for the state health department identifies a three-month spike in lead levels in Flint during the previous summer, after the switch to river water. She recommends further investigation in an email to her bosses, but they decide it was a seasonal anomaly.
Aug. 31: Virginia Tech Professor Marc Edwards, who is leading students in testing Flint water, reports that 42 percent of 120 samples had elevated lead levels, and 20 percent had levels that require water systems to take action. Edwards explains that the water from the river is "very corrosive" and is leaching lead from plumbing in the city's homes.
Sept. 24: Dr. Mona Hanna-Attisha, a pediatrician at Hurley Children's Hospital, says a comparison a blood samples she undertook shows a jump in lead poisoning in Flint's children. State officials told the Detroit Free Press their own samples don't show the same increase.
Oct. 1: State officials announce that a new analysis of their data shows Hanna-Attisha is correct: more children have lead in their blood since the water switch.
Oct. 2: Gov. Snyder announces the state will buy water filters and test lead in schools. Within a week, he will recommend that Flint start using water from Detroit, and $6 million to help the city switch back is eventually approved.
Oct. 16: Flint switches back to Detroit water.
Nov. 3: Karen Weaver, who ran for mayor on a promise of solving the water crisis, is elected over Walling.
Jan. 5: Snyder declares a state of emergency in Flint. The Department of Justiceopens an investigation into the debacle.
Jan. 12: Under increasing fire, Snyder calls out the National Guard to distribute bottled water and filters in Flint.
Jan. 13: The crisis expands to include Legionnaires' disease as officials reveal a spike in cases, including 10 deaths, after the city started using river water.
Jan. 15: The Michigan attorney general opens an investigation to see if any laws were broken in the handling of the crisis. A state legislator points out that he asked the AG to launch a probe three months earlier and was rebuffed.
Jan. 16: President Barack Obama signs an emergency declaration and orders federal aid for Flint, two days after a request from Snyder.
Jan. 17: Democratic presidential candidates Hillary Clinton and Bernie Sanders focus on Flint and criticize Snyder during a televised debate.
Jan. 18: Snyder admits in an interview with the National Journal that Flint could be his Hurricane Katrina. "It's a disaster," he concedes.
This timeline first appeared on NBCNews.com.