Toni Preckwinkle has seen a “significant drop in favorability and a clear drop in vote share” since being dragged into the federal corruption scandal that threatens to bring down Ald. Edward Burke (14th) — and Susana Mendoza is the chief beneficiary.

That’s the bottom line of a new poll of 600 likely Chicago voters conducted during a five-day period that ended Tuesday. The poll, by the Global Strategy Group, Gov. J.B. Pritzker’s pollster, was taken for Mendoza’s campaign.

It shows Preckwinkle’s “net favorability has dropped by 26 points” over the last month and that she is “now underwater at minus 10,” according to a memo of “key findings” prepared by Mendoza’s pollster and released by the state comptroller’s mayoral campaign.

“Net favorability” is a term pollsters use. It’s figured by subtracting the percentage of voters who rate a candidate favorably from the percentage of those surveyed who view them unfavorably.

Preckwinkle’s loss came from an 11-percentage-point drop in her favorability rating — from 47 percent in December to 36 percent this month — and from a 15-percentage-point increase — to 46 percent — in the number of voters who view her as “unfavorable.”

“She is now underwater at minus 10,” the memo says of Preckwinkle.

The memo does not say how that compares to Mendoza’s net favorability. Nor does it say how Mendoza’s standing with voters has changed over the last month.

When Global Strategy Group conducted a similar poll for Mendoza Dec. 10-13, Preckwinkle led the crowded field of mayoral candidates vying to replace Mayor Rahm Emanuel with 19 percent of the vote to Mendoza’s 11 percent and Bill Daley’s 8 percent.

The newer poll, conducted Jan. 11-15, shows Preckwinkle and Mendoza tied for the lead at 11 percent. Daley now stands at 9 percent. That’s a disappointing 1 percentage-point gain for Daley, even though his television commercials hammering away at the issues of crime, taxes and downtown-centric development have been blanketing the airwaves for weeks.

The poll has a margin for error of plus or minus 4 percentage points — and, given that margin, the results mean Preckwinkle, Mendoza and Daley are essentially tied.

In a head-to-head matchup between the two frontrunners, however, Mendoza now has a comfortable lead, 43 percent to Preckwinkle’s 30 percent, with the rest of those surveyed undecided.

In December, Mendoza had 39 percent to Preckwinkle’s 38 percent — again, essentially a tie, given the margin of error.

A runoff between Mendoza and Daley would yield similar results and is virtually unchanged since December, the pollster said. Mendoza now leads with 45 percent to Daley’s 30 percent.

“Given Mendoza’s name ID advantage, top vote-getting status in a multi-candidate race and significant lead in run-off scenarios with either Preckwinkle or Daley, Mendoza continue to be well-positioned to become the next mayor of Chicago,” the memo states.

The Mendoza campaign refused to release the entire poll or the wording of the questions asked. Nor would they say how other candidates fared. Sources said voters surveyed were not asked so-called “push” questions, in which positives and negatives of individual candidates are mentioned as part of the poll.

The firm’s most recent poll for Mendoza was conducted after Burke, former longtime chairman of the City Council’s Finance Committee, was charged with attempted extortion for allegedly shaking down a Burger King franchise owner for legal business and for a $10,000 campaign contribution to Preckwinkle’s re-election campaign as county board president.

Burke held a fundraiser for Preckwinkle in his home in January 2018, and the Burger King franchise owner was asked to attend. Preckwinkle initially refused to return the $116,000 she raised there, only to reverse field and promise to return every last dollar after charges against Burke were filed.

Desperate to turn the page from the Burke scandal, Preckwinkle hit the airwaves last week with a television commercial highlighting her role in exposing the cover-up of the police shooting of Laquan McDonald.

But that effort also backfired. Mayoral candidates and community activists alike accused Preckwinkle of claiming credit that rightfully belonged to investigative reporters and a youth-based movement of activists inflating her role to distract attention from the Burke scandal that has undermined her reputation as a reformer.