(CHICAGO) On a crisp morning, a bundled-up Juliana Stratton went door to door in the South Shore neighborhood, making her pitch for why voters should pick her over incumbent Rep. Ken Dunkin in Illinois’ 5th House District — a race that some observers say could affect the balance of power in Springfield, the Sun-Times is reporting.

When someone opened the door, Stratton, a Democrat, introduced herself and stuck to the same, brief message.

“It’s a really important race,” said Stratton, a lawyer and former senior policy adviser to Cook County Board President Toni Preckwinkle. “My opponent has missed some really important votes that are devastating our communities.”

Stratton, director of the University of Illinois at Chicago’s Center for Public Safety and Justice, said almost nothing about herself. There was probably no need. For most of the campaign, this pivotal House race has been about Dunkin — the renegade Democrat who has defied House Speaker Michael Madigan on two key votes and cozied up to Republicans, taking a $500,000 donation from a Republican-linked group. “Sellout” and “opportunist” are among the more polite words Dunkin’s detractors have used to describe him in recent weeks.

Political observers say Dunkin and Stratton are merely bit players in a larger war between Gov. Bruce Rauner and Madigan. A Stratton win, they say, is vital for Madigan to ensure a veto-proof majority.

For his part, Dunkin says he did what voters fed-up with the Springfield gridlock wanted — he stepped across the aisle, helping pave the way for Rauner compromises that restored funding for programs benefiting the state’s most vulnerable citizens.

“This is probably going to be a referendum for or against Dunkin,” said Dick Simpson, a professor of political science at UIC and a former city alderman. “Stratton makes a good candidate on her own, but it is probably a referendum on Dunkin and him opposing Madigan.”

That was before Monday, when President Barack Obama took the unusual step for a sitting president of making an endorsement in a state legislative primary race — backing Stratton. Now voters have a reason to vote for the challenger, said Constance Mixon, an associate professor of political science at Elmhurst College.

Mixon says Obama’s endorsement could be a game changer, particularly among African-American voters who fondly remember the president from his days as a South Side state senator.

“His getting involved in this election is unprecedented, and it can make a difference,” Mixon said.

Adding to Dunkin’s problems, Mixon said, are allegations that surfaced last week of possible voter fraud. Secretary of State Jesse White and Ald. Pat Dowell [3^rd] — both Stratton backers — held a news conference, accusing Dunkin of buying early votes in the battle to keep his seat. The Cook County state’s attorney’s office is looking into the matter. A spokesman for Dunkin has called the allegations “baseless accusations.”

Dunkin was a low-profile state legislator in a narrow district that runs from the Near North Side to the South Side’s Grand Crossing neighborhood. Then last year, he skipped two key votes — putting him at odds with Madigan and his fellow Democrats. Last month, Dunkin’s political campaign also received what may be the largest single Illinois legislative primary donation on record — $500,000 from a conservative group.

To those saying he’s a sell-out, Dunkin, who is African-American, said he’s rightly rebelling against Madigan, who he has compared to a slave owner.

“The Mike Madigan mentality of his plantation politics is real,” Dunkin told the Chicago Sun-Times Editorial Board in February.

Dunkin did not respond to several requests for an interview for this story.

Dunkin’s flair for the dramatic backfired spectacularly about a month ago, when Obama addressed the General Assembly in Springfield. When the president began speaking about the importance of bi-partisanship, Dunkin stood up and clapped, presumably suggesting Obama was speaking about him. Obama told Dunkin to sit down, and howls of laughter filled the chamber.

Stratton said voters are taking note of Dunkin’s behavior.

“What I’m hearing is that they are very concerned about his new alliance with … Rauner,” Stratton said. “When they see how much money that Rep. Dunkin received from Republican sources, they are really concerned about whether they can trust him to make decisions in their best interest.”

But money is also pouring into Stratton’s campaign — mostly from unions.

“The thing they can’t make as an argument is that I’m receiving money from Republican sources,” Stratton said. “The money I’m receiving to help me run a successful campaign is from fellow Democrats.”

In addition to the Obama endorsement, Stratton’s has the support of a number of high-profile Democrats, including Preckwinkle and Chicago Teachers Union President Karen Lewis. Stratton said she’s getting union help on the ground and in making phone calls to potential voters. A Madigan spokesman said last week that the speaker isn’t involved in the campaign.

Even so, Stratton is taking on an opponent who won more than 80 percent of the vote in 2014. That’s why in early march, dressed in a full-length puffy coat and a woolen hat, she was going door to door — hitting a block in the South Shore neighborhood she’d walked twice before during the campaign.

“Any time you’re running against an incumbent, it’s an uphill battle,” Stratton said. “People know the name of the incumbent, whether he or she has provided good representation or not. So that’s what I’m coming up against.”