Former Trump campaign manager Paul Manafort and his little-known business partner Rick Gates were indicted Monday by a federal grand jury on 12 charges, including money laundering and conspiracy against the United States.

While Manafort became a household name when he joined Donald Trump's presidential campaign last May, Gates has flown under the radar. Few Americans know anything about the longtime lobbyist who was making frequent visits to the White House as recently as March.

Gates' relationship with Manafort stretches back decades. The two worked together at Black, Manafort, Stone and Kelly, a consulting firm formed in 1980 at which another close Trump associate, Roger Stone, served as partner. Gates is said to have connected with Manafort initially when he was an intern at the firm.

Stone did not respond to multiple requests for comment about the arrest of either of his former business partners on Monday.

The former intern eventually became Manafort's top deputy, working with the veteran lobbyist to serve several pro-Russia clients over the years. When former Ukrainian Prime Minister Yulia Tymoshenko sued Manafort in 2011 for racketeering, Gates was named as an agent of a Ukrainian oligarch.

Though an American judge tossed the lawsuit in 2015, legal documents from the case were obtained by special counsel Robert Mueller and his team as part of their investigation into Russian election meddling.

Following the inauguration, Gates went to work for America First Policies, an outside group formed by former Trump campaign hands to support the president's agenda. He was forced to leave the group in late March – days after former FBI Director James Comey confirmed the agency was investigating alleged ties between the Kremlin and Trump associates – due to renewed scrutiny of his relationship with Manafort.

A spokeswoman for America First Policies declined to comment on Gates' arrest when reached by the Washington Examiner Monday.

Gates went on to work for billionaire investor Tom Barrack, a longtime friend of the president's, after he was booted from America First, the Daily Beast reported earlier this year. He joined Barrack for several visits to the White House last spring, angering some West Wing staffers who described Gates as someone Trump despised.

Gates also served as a wrangler at the 2016 Republican National Convention, where he helped whip rules committee members against attempts to amend party rules that could have blocked Trump from receiving the nomination.

"Our goal is to destroy them," Gates told CNN at the convention, referring to those who were behind anti-Trump efforts.

Earlier this year, the Trump campaign instructed current and former aides to preserve all documents and emails, but to pay particular attention to memos related to several Trump associates — two of whom were Manafort and Gates.

The document preservation memo stoked speculation that the two lobbyists-turned-campaign-hands were under the special counsel's scrutiny.

After working closely with Manafort in international consulting work for a number of years, Gates reportedly joined his mentor as an investment partner in the 2000s, further entangling their finances and legal fates. Neither Gates nor Manafort properly disclosed their international political work under the Foreign Agents Registration Act, which requires lobbyists for foreign powers to inform the government of their activities.

Failure to register under FARA numbered among the charges contained in Special Counsel Robert Mueller's indictment that was unsealed on Monday.