Serious allegations of voter fraud surfaced Sunday within a high-stakes Illinois House campaign, catching the attention of Cook County prosecutors.

Secretary of State Jesse White and Ald. Pat Dowell (3rd) appeared at a South Side press conference to accuse Rep. Ken Dunkin of buying early votes in the battle to keep his 5th District seat in the state House of Representatives. Dunkin’s opponent, Juliana Stratton, also stood nearby as Dowell shared what she claimed is video evidence of Dunkin’s alleged scheme — purportedly shot by people who infiltrated the vote-buying operation and cast ballots in exchange for “crisp $50 bills.”

“This is a violation of all laws of human decency, and shame on Mr. Dunkin and his organization for doing this,” White said.

OBAMA: President endorses Stratton in campaign against Dunkin

Dunkin could not be reached to answer specific questions about the allegations, but a spokesman responded with this emailed statement: “Dowell’s baseless accusations are consistent with the desperate tactics previously used by the (House Speaker Michael) Madigan-led Stratton campaign. While Rep. Dunkin is working on issues such as abolishing red-light cameras, his opponent is still up to the same dirty tricks that have defined her campaign.”

Meanwhile, a spokeswoman for Cook County State’s Attorney Anita Alvarez confirmed that Dowell reached out to Alvarez’s election unit Saturday. The state’s attorney’s office is now “looking into the matter,” spokeswoman Sally Daly said.

Even with less than two weeks to go until Illinois’ primary election, the allegations amount to more than “normal dirty tricks,” according to Kent Redfield, a professor emeritus of political science at the University of Illinois Springfield.

“If true, then this is an extremely serious situation,” Redfield said.

Dunkin, D-Chicago, has irritated members of his own party by denying Madigan key votes in Springfield. His political fund also landed the largest single campaign contribution in state history — $500,000 from a political action committee backed by supporters of Republican Gov. Bruce Rauner.

Campaign workers noticed a larger-than-normal early voter turnout Saturday at the Chicago Bee Branch library, Dowell said. So four unnamed volunteers decided to go undercover. Dowell claims voters were being vetted at Dunkin’s campaign headquarters in the 2900 block of South Wabash, told to vote for Dunkin, taken to the library and returned to Dunkin’s campaign office to collect $50 or $100.

The four people who went undercover cast ballots, collected money and have since spoken to Chicago Police, Dowell said.

The alderman’s staff shared three videos Sunday they said captured the alleged sting operation. The shaky recordings largely appear to show a group of men speaking with campaign workers and, at times, discussing the possibility of getting paid for their votes as they made comments like “politics ain’t s – – – , is it?”

But in one scene played for reporters Sunday, a man appears to be handing out money in a room with Dunkin signs on the walls.

Asked about the effect Dunkin’s alleged activity — and Dowell’s sting operation — could have on the election, White said, “you cannot take back the votes that have been cast.”

“I think that based on what we’ve been able to see thus far, the authorities should step in, admonish Ken Dunkin and his organization for participating in this kind of activity,” White said.