That all changed during a seven-day span in late September when Munger's campaign received $5,323,500, largely from two Chicago-area businessmen with close ties to Gov. Bruce Rauner.
Hedge fund manager Ken Griffin donated $3 million to Munger just two days after she received $2 million from packaging and supply magnate Dick Uihlein. The state GOP also donated $55,500 during that span, and Munger's husband, John, contributed $260,000.
Munger's campaign has taken in nearly $6.5 million since June 30, according to state campaign finance records through Wednesday. The money came from 56 separate contributions. That includes a $1 million infusion from Rauner's campaign earlier this week.
Rauner tapped Munger, of Lincolnshire, two years ago to fill the position left vacant by the death of GOP stalwart Judy Baar Topinka. The race this year is for the remaining two years on Topinka's term. The comptroller is responsible for paying the state's bills.
Even after Munger turned over $3 million of her campaign's windfall to the state party, she was left with $3.4 million in contributions, more than three times what Mendoza's campaign had raised since the end of June.
In that same time span, Mendoza, of Chicago, has raised $1,004,650 from 130 contributions. Almost $640,000 of those contributions came from union groups, campaign finance records show.
Munger complained about Mendoza's political history, first as a legislator and now Chicago city clerk, while defending her campaign's own donors. Munger's recent television ads depict Mendoza as a career politician who will receive two pensions for her work with the state and the city.
"In order to run a statewide race, you need funding, and it's very hard to raise money for me as a relative newcomer to state government," Munger said during a recent visit with the Daily Herald editorial board. "The money that has come to me was transferred out immediately to help out other candidates in the state and certainly (some donors) are people who are friends of the governor, but they are also people who are business leaders who want good government in Illinois. I'm just following the laws the Democrats passed."
Munger also noted she does not participate in the state's pension program or take advantage of the state health insurance benefits.
For her part, Mendoza defended her political career and said Munger's campaign contributions from friends of the governor show she's not as independent as she claims.
"You don't need a novice who has to take direction," Mendoza said. "I got started (in politics) very young because my life was different from hers as a kid. I wasn't born with a silver spoon. I didn't marry into wealth or anything. My opponent shames my service to this state of over 15 years, but I'm super proud of it."
Mendoza touts her efforts as city clerk to streamline services, cut costs and increase revenues through modernization of the city's vehicle sticker program. Some government finance watchdog groups were calling for the office to be cut before Mendoza took over but have lauded her efforts since then.
"That's what you can do when you're a hardworking, vision-oriented person who can execute on that vision, and that's the type of leadership I'll bring to Springfield," she said.
Munger said her two years in office have been the most challenging any comptroller has ever faced because the state has been working without a budget the majority of the time. She said she has stood up to outside influences and even the governor who put her in office. The absence of a budget is a disservice to the state's residents, she said.
"Really it's a shirking of the responsibility of all involved," Munger said. "It's their duty under the Constitution to pass a budget, and they haven't done it."
Libertarian Claire Ball and the Green Party's Tim Curtin are also vying for the seat.
The election is Nov. 8.