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Conservative state Sen. Darren Bailey's convincing victory in Illinois' Republican gubernatorial primary is a big win for former President Donald Trump – and for Democrats.

The former president, who nearly a year and a half removed from the White House remains the most popular and influential politician in the GOP, endorsed Bailey on Saturday as he headlined a large rally in Illinois.

Donald Trump Illinois

State Sen. Darren Bailey greets Donald Trump after receiving an endorsement during a Save America Rally at the Adams County Fairgrounds on June 25, 2022, in Mendon, Illinois. (Michael B. Thomas/Getty Images)

Bailey's victory gives Trump some bragging rights after the former president suffered setbacks in other high-profile Republican gubernatorial showdowns so far this primary season.

But Bailey's nomination is also a win for Democratic Gov. J.B. Pritzker and the Democratic Governors Association, who combined spent tens of millions of dollars to boost Bailey over moderate Republican Mayor Richard Irvin of Aurora, a city in metropolitan Chicago. 

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Democrats viewed Bailey as the weaker general election candidate in November compared to Irvin, who was helped by tens of millions in support from billionaire conservative Ken Griffin, the CEO of Citadel, the multinational hedge fund and financial services behemoth.

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Bailey easily topped Irvin and cryptocurrency entrepreneur Jesse Sullivan, who were his top two rivals in a field of six GOP candidates.

In the wake of Friday's blockbuster opinion by the conservative majority of the Supreme Court overturning the landmark half century old Roe v. Wade ruling, abortion is expected to be a top issue in the Illinois governor's election. Bailey opposes abortion in nearly all cases, while Pritzker wants to make Illinois a safe haven for women from other states where abortion is now illegal.

Illinois Gov. J.B. Pritzker

Illinois Gov. J.B. Pritzker greets spectators during the Chicago Pride Parade, Sunday, June 26, 2022. (AP Photo/Jon Durr)

"Darren Bailey is a MAGA extremist who’s threatening to drag Illinois backwards. With his far-right, out-of-touch stances on critical issues from abortion to guns to COVID, a would-be Governor Darren Bailey is a danger to all Illinoisans," DGA executive director Noam Lee charged.

Trump's last minute endorsement of Bailey - which helped the Democrats' mission to boost the state senator at the expense of Irvin - was quietly celebrated by Democrats.

"Trump loves nothing more than a bandwagon, and Democrats were more than happy to provide him one to jump on for Darren Bailey. The more rallies in Illinois this fall, the better," a Democratic strategist who works on gubernatorial races told Fox News.

But Trump world disagrees with any talk of him taking the Democrats' bait by backing Bailey.

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Pointing to far right state lawmaker Ron Hanks of Colorado - whom Democrats unsuccessfully tried to boost in Tuesday's GOP Senate primary - a Republican strategist in Trump's political orbit told Fox News: "Ron Hanks really was unelectable. I don't think anyone sees Darren Bailey the way they saw Ron Hanks."

"I think in the right atmosphere Illinois will be competitive," added the strategist, who asked to remain anonymous to speak more freely.

Trump scored another victory in Illinois, as Rep. Mary Miller, a first-term representative and Trump supporter, defeated fellow Republican Rep. Rodney Davis in the GOP primary in the newly drawn 15th Congressional District. 

Donald Trump Illinois Mary Miller

Rep. Mary Miller gives remarks during a rally with former President Donald Trump at the Adams County Fairgrounds on June 25, 2022, in Mendon, Illinois. (Michael B. Thomas/Getty Images)

Davis, who for a decade has represented the neighboring 13th District, ran against Miller for the new, heavily red seat in the central part of the state, which contains large swaths of his current district. 

Davis was one of 35 House Republicans who last year voted for a bipartisan and independent commission to investigate the Jan 6, 2021 deadly attack on the U.S. Capitol by right wing extremists and other Trump supporters who aimed to disrupt the congressional certification of President Joe Biden’s 2020 election victory. The bill to create the commission was downed in the Senate and House Democrats eventually set up a select committee of mostly Democrats to investigate the storming of the Capitol.

TRUMP DEALT MORE SETBACKS IN GEORGIA AS CANDIDATES HE BACKED TROUNCED IN GOP PRIMARY RUNOFFS

Trump took aim at Davis and praised Miller at Saturday's rally in the district. On the eve of the rally, Miller charged in an interview with Fox News that Davis "stabbed President Trump in the back multiple times and the people in the 15th district don't appreciate it. Voting for the January 6 Commission has outraged people."

Rep. Rodney Davis of Illinois

GOP Rep. Rodney Davis speaks at the 2021 Illinois State Fair, on Aug. 19, 2021 in Springfield. (Rodney Davis Campaign)

Miller’s win is the second victory by a Trump-endorsed candidate in a House member-on-member matchup. In May, Republican Rep. Alex Mooney, who was backed by the former president, defeated fellow GOP Rep. David McKinley in their party’s primary for West Virginia’s 2nd Congressional District. 

The former president's political wins on Tuesday follow the defeat of a handful of Trump-backed candidates in recent primaries that grabbed plenty of media attention.

"It's definitely a good night for him," noted the strategist with ties to the Trump world. "The Mary Miller race was a very big one."

But the operative added that "I don't think anyone sees the races he lost as a sign of waning power. It was just bad endorsements."

While Davis went down to defeat, another House Republican who voted for the bipartisan Jan. 6 commission easily defeated a primary challenger.

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In Mississippi's 3rd Congressional District, two-term GOP Rep Michael Guest topped challenger Michael Cassidy by a more than two-to-one margin in a primary runoff election.

Cassidy had repeatedly attacked Guest for voting for the commission, but Trump declined to take sides in the race.