Marking the first concrete threat to Cook County politicians who support the pop tax, critics of the measure have formed a political-action committee to raise money for challengers in next year’s elections.

The new group — called Citizens for a More Affordable Cook County — quietly filed paperwork to form as a campaign committee with Illinois elections officials last month, records show.

Underscoring the spreading distaste for the sweetened beverage tax, the new PAC has ties to the Democratic Party — the same party that backed the tax itself.

The PAC says it could fund challengers to the eight County Board commissioners who voted for the tax. But in a statement to the Sun-Times on Thursday, the group pointedly avoided saying whether it would back a challenger to Cook County Board President Toni Preckwinkle, who’s up for a third term in 2018.

Polls show the tax, which applies to sugar-sweetened and artificially sweetened beverages alike, is hugely unpopular and has put a severe dent in Preckwinkle’s job-approval ratings, with speculation growing that she will face a challenger in the March Democratic primary.

It’s not yet clear who will provide funding for the new political campaign committee. State records show the group’s treasurer is Michael Kasper, a well-known figure in Illinois political circles.

Kasper is the longtime top attorney for the state Democratic Party and its chairman, Illinois House Speaker Michael Madigan, D-Chicago. Kasper probably is best known for successfully representing Rahm Emanuel against claims he failed to meet the residency requirements to run for mayor in 2011.

Michael Kasper, representing Rahm Emanuel at a 2010 meeting of the Board of Election Commissioners of the City of Chicago. (File photo by John H White/Chicago Sun-Times.)

Kasper also is a lobbyist at City Hall and in Springfield — where his long client list includes the Washington-based American Beverage Association. The association has opposed the county’s pop tax.

Preckwinkle has dismissed critics of the pop tax as special-interest groups representing “Big Soda.”

Citizens for a More Affordable Cook County describes itself as “a community PAC that receives support from businesses, their customers and residents and will be a voice for the millions of Cook County citizens devastated by unfair, regressive and skyrocketing taxes.”

The group says it will support County Board candidates “who are committed to standing up for the small businesses and working families hurt by massive tax increases imposed by Cook County’s current commissioners over the past several years.”

The statement from the new group cited the high sales tax in the county. Preckwinkle was first elected in 2010, unseating incumbent Todd Stroger, and she carried out a campaign promise to reverse a sales-tax increase that was enacted by her predecessor. But the sales tax rate since has gone back up again, at Preckwinkle’s urging.

And last year, Preckwinkle cast the tie-breaking vote when the board deadlocked on the pop tax she proposed. The measure went into effect last month, though opponents recently introduced a proposal to repeal it.

Preckwinkle and other proponents of the tax argue that they were motivated by public-health concerns.

Officials initially projected the tax would generate $225 million a year in revenue for a county government that faced a budget deficit. The project has since been adjusted downward, to $200 million.

“We strongly believe the reasons behind the tax have not changed and neither has our approach,” Preckwinkle administration spokesman Frank Shuftan said Thursday.

“The revenue is necessary to preserve vital public health and public safety programs and services, and reduction in the consumption of such beverages will lead to healthier lives for our residents.”

The chairman of Citizens for a More Affordable Cook County is Jeremy Jansen of Chicago, records show. He was Midwest director of Hillary Clinton’s 2016 campaign for president.

The group alleges the pop tax has caused “an immediate drop in sales for many businesses.”

“The tax is especially harmful to communities on the border of other counties or states that don’t have such taxes,” the PAC said in its statement.

Of the eight commissioners who joined Preckwinkle in voting for the tax in November, five recently told the Sun-Times they continue to stand by their votes. Those five were Jesus “Chuy” Garcia, Larry Suffredin, John Daley, Stanley Moore and Deborah Sims.

Three other commissioners who had voted for the pop tax — Luis Arroyo Jr., Jerry “Iceman” Butler and Edward Moody — did not return calls seeking comment when asked for their current stands on the matter.

Sources say Sims, Moore and Moody could be the most likely to face challengers backed by the new PAC because stores in their districts are close enough to other counties that they are losing business to competitors across county lines because of the pop tax.

All eight commissioners who voted for the tax are Democrats.

Tuesday was the first day to circulate nominating petitions, and Dec. 1 is the deadline to file paperwork for the March 20 primary.