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TALLAHASSEE (CBSMiami/NSF) – Longtime Democratic Congresswoman Corrine Brown has been indicted on charges that she and a top aide used a sham education charity to pay for personal expenses and luxurious events, allegations that pose the most serious challenge yet to her 23-year congressional career.

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Brown and Elias “Ronnie” Simmons, her chief of staff, pleaded not guilty to all 24 counts in the indictment, 22 of which deal with Brown. Federal prosecutors say the two worked with Carla Wiley, a Virginia woman who reached a plea deal with the government in March, to set up “One Door for Education” and use it “as a personal slush fund,” in the words of Assistant Attorney General Leslie Caldwell.

Brown is charged with conspiracy, mail and wire fraud, concealing income on financial disclosures that members of Congress are required to file, and four counts of violating tax laws.

“Congresswoman Brown and her chief of staff are alleged to have used the congresswoman’s official position to solicit over $800,000 in donations to a supposed charitable organization, only to use that organization as a personal slush fund,” Caldwell said in a prepared statement announcing the indictment. “Corruption erodes the public’s trust in our entire system of representative government.”

But Brown, a pugnacious congresswoman known for fiercely defending her district and her legacy, insisted to reporters Friday that she is innocent. The congresswoman, who has built her identity around constituent service, said she would “let the work I’ve done speak for me.”

“My heart is just really heavy,” she said. “This has been a very difficult time for me, my family, my constituents. But I’m looking forward to a speedy day in court to vindicate myself. … We’ve got the rest of the story. So I’m looking forward to presenting the rest of the story.”

In a sign of the fallout from the indictment, U.S. House Democratic Leader Nancy Pelosi announced that Brown had stepped aside from a high-ranking post on the House Veterans’ Affairs Committee, in line with caucus rules.

“For more than two decades, Congresswoman Brown has served her constituents in Florida with passion and energy. She has been a champion for America’s veterans,” Pelosi said. “The charges against Congresswoman Corrine Brown in the indictment today are deeply saddening.”

Speculation about a grand jury investigation into One Door for Education, and the implications for Brown’s political future, has churned through the political gossip mill for months. All the while, she has fought a pitched battle against the redrawing of her district under a voter-approved ban on political gerrymandering and framed the dual battles as part of an orchestrated campaign to drive her from office.

Brown, 69, is facing what could be her toughest re-election battle in years. Her district, drawn in 1992 to give African-American voters in North and Central Florida a chance to elect a candidate of their choice, has traditionally run north-south, with the most recent version winding from Jacksonville to Orlando. But following the ban on gerrymandering, courts ordered the seat to be reoriented. It now cuts across the northern part of the state, going from Jacksonville in the east to Gadsden County in the west, traveling through Tallahassee along the way.

One of her attorneys lacerated the federal government Friday for not agreeing to push back the arraignment to accommodate Brown’s congressional schedule — she missed several votes Friday — and for leaks from the criminal investigation. Brown’s indictment was widely reported Thursday, even though her attorneys didn’t see the charges until the congresswoman turned herself in Friday.

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“Congresswoman Brown is the subject of an indictment today, but in reality, she has endured a one-sided inquisition in the court of public opinion for over one year. … The manner in which the government has handled these proceedings leads to the inescapable conclusion that it desires to improperly influence the upcoming election and undermine the legislative process,” attorney Betsy White said.

According to the indictment, Brown and Simmons worked with Wiley to raise more than $800,000 for One Door — which was falsely portrayed as a 501(c)(3) non-profit — and then used an array of financial transfers to funnel the money to themselves and one of Brown’s relatives.

In addition to car repairs, flights and other expenses, prosecutors say the money was used to pay for a golf tournament in Ponte Vedra Beach in Brown’s honor and luxury boxes at a Beyonce concert and at an NFL game in Washington, D.C. Meanwhile, the organization only gave out $1,200 in scholarships, its supposed purpose.

Even before the indictment, Brown faced a serious challenge in the Aug. 30 Democratic primary from former state Sen. Al Lawson of Tallahassee. Lawson did not immediately respond to a request for comment Friday. In a post to his Facebook page Thursday, as word of the indictment began to circulate, Lawson called the situation “unfortunate” but said he was focused on the campaign.

“I promise all the voters of the 5th Congressional District I intend to carry the torch of equality, decency and honesty to Congress and to make everyone proud,” Lawson wrote.

A recent poll by the Public Opinion Research Laboratory at the University of North Florida, based in Jacksonville, showed Brown with a three-point lead over Lawson, 30 percent to 27 percent, with 4 percent going to little-known LaShonda Holloway. The incumbent’s lead was well within the poll’s margin of error of 4.9 percentage points.

Brown held a resounding lead in the portion of the district located in Duval County, where the incumbent drew 52 percent of the vote, but she trailed Lawson by double digits in the rest of the district.

Mike Binder, faculty director of the poll, said Friday that voters in the western parts of the district had mostly been introduced to Brown through the fight against the redistricting plan, followed by the criminal charges.

“The voters have seen that side or her, and now they’re seeing this side of her, which I can’t imagine is going to be good for likely voters,” he said.

Binder also noted that Brown has to deal with the criminal charges, which could lead to up to 357 years in prison and $4.8 million in fines, though the maximum sentences are rarely given to first-time offenders as a practical matter.

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The News Service of Florida’s Brandon Larrabee contributed to this report.