WASHINGTON >> A former senior adviser to President Donald Trump’s election campaign pleaded guilty today to federal conspiracy and false-statements charges, saying he will now cooperate in the special counsel’s Russia investigation.

The plea by Rick Gates revealed that he will help special counsel Robert Mueller’s investigation in “any and all matters” as prosecutors continue to probe the Trump campaign, Russian election interference and Gates’ longtime business associate, Paul Manafort.

With his cooperation, Gates gives Mueller a witness willing to provide information on Manafort about his finances and political consulting work in Ukraine, and also someone who had access at the highest levels of Trump’s 2016 presidential campaign.

Gates, 45, of Richmond, Virginia, made the plea at the federal courthouse in Washington. He admitted to charges accusing him of conspiring against the U.S. government related to fraud and unregistered foreign lobbying as well as lying to federal authorities in a recent interview.

The plea came a day after a federal grand jury in Virginia returned a 32-count indictment against Gates and Manafort, Trump’s former campaign chairman, accusing them of tax evasion and bank fraud.

The indictment in Virginia was the second round of charges against Gates and against Manafort, who has denied any wrongdoing. The two men were initially charged last October with unregistered lobbying and conspiring to launder millions of dollars they earned while working on behalf of a pro-Russian Ukrainian political party.

Gates’ decision marks the fifth publicly known guilty plea in the special counsel probe into possible collusion between the Trump campaign and the Kremlin during the 2016 campaign.

The plea also comes quickly on the heels of a stunning indictment last week that laid out a broad operation of election meddling by Russia, which began in 2014, and employed fake social media accounts and on-the-ground politicking to promote Trump’s campaign, disparage Hillary Clinton and sow division and discord widely among the U.S. electorate.

The charges to which Gates is pleading guilty don’t involve any conduct connected to the Trump campaign. They largely relate to a conspiracy of unregistered lobbying, money laundering and fraud laid out in his indictments.

But his plea does newly reveal that Gates spoke with the FBI earlier this month and lied during the interview. That same day, his attorneys filed a motion to withdraw from representing him for “irreconcilable difference.”

The court papers accuse Gates of lying about a March 19, 2013, meeting involving Manafort, a lobbyist and a member of Congress. Gates said the meeting did not include discussion of Ukraine, when in fact prosecutors say it did.

The charges don’t name the lobbyist or the lawmaker but filings with the Justice Department show Manafort and lobbyist Vin Weber of Mercury Public Affairs met with Rep. Dana Rohrabacher, R-Calif., on that date as part of a lobbying campaign on behalf of Ukrainian interests.

Manafort said today in a statement that he maintains his innocence.

“I had hoped and expected my business colleague would have had the strength to continue the battle to prove our innocence. For reasons yet to surface he chose to do otherwise,” Manafort said. “This does not alter my commitment to defend myself against the untrue piled-up charges contained in the indictments against me.”

In court filings over the past few months, Gates gradually began to show the strain the case was placing on him and his family.

As Gates was kept on house arrest, he frequently pleaded with U.S. District Court Judge Amy Berman Jackson for leniency to attend sporting events with his four children. Even today, ahead of his plea, Gates had asked the judge to let him take his children to Boston for spring break so they could “learn about American history in general, and the Revolutionary War in particular.”

On Thursday night, Gates emailed a brief letter to friends and family, telling them of his decision to plead guilty, Republican lobbyist Jack Burkman said.

“It’s sad,” said Burkman, who had hosted a fundraiser for Gates’ legal defense fund.

Under the terms of the plea, Gates is estimated to face between 57 and 71 months behind bars. Prosecutors may seek a shortened sentence depending on his cooperation.

Gates served on the Trump campaign at the same time that Manafort, Donald Trump Jr. and Jared Kushner met with a team of Russians in Trump Tower in June 2016. He was also in the top ranks of the campaign when then-Sen. Jeff Sessions held a pair of undisclosed meetings with Russian ambassador to the U.S. Sergey Kislyak.

For a few months in 2016, Gates was indispensable to Trump, leading the ground effort to help Trump win the Republican nomination and flying from state to state to secure Republican delegates in a scramble that lasted all the way until the Republican National Convention in Cleveland.

But his power and influence waned once Trump fired Manafort in August 2016 after The Associated Press disclosed how Gates and Manafort covertly directed a Washington lobbying campaign on behalf of Ukrainian interests.

Gates survived his mentor’s ouster and worked through the election on Trump’s inaugural committee — but among Trump aides he earned the nickname “the walking dead.” Gates also worked briefly with the outside political groups supporting Trump’s agenda, America First Policies and America First Action, but was pushed out of that job last year.

Gates was working for Tom Barrack, a close friend of Trump’s, when he was indicted last October.