The charges unsealed Thursday compound both Manafort and Gates' already immense legal troubles, and may be an attempt by special counsel Robert Mueller's team to squeeze the men further.
Sources have told NPR in recent weeks that Gates, who is now struggling to pay his mounting legal fees, may be in the process of negotiating a guilty plea.
Manafort and Gates are two of the most prominent members of Trump's former campaign to face criminal charges as part of the special counsel's investigation into possible coordination between Trump associates and Russia's attack on the 2016 election.
Former national security adviser Michael Flynn and former campaign foreign policy aide George Papadopoulos have both pleaded guilty to lying to the FBI about their contacts with Russians.
Last week, Mueller's office unveiled charges against 13 Russian nationals and three Russian entities for their alleged role in the Kremlin's interference operation.
The charges Manafort and Gates face, on the other hand, stem from political consulting work they did for a pro-Russian political party in Ukraine — and allegedly attempting to shield their earnings from that work from U.S. authorities. Many of the alleged crimes date back to years to before the 2016 campaign, but some continued past election day.
The charges do not include allegations that either man colluded with a foreign attack on the election.
In its court filing Thursday, the special counsel's office said it brought the new charges before the grand jury in the Eastern District of Virginia because "our current evidence venue for these charges does not exist in the district of Columbia."
The new indictment, which was widely expected, appeared amid questions about Gates' legal team. His lawyers have requested to withdraw from the case. Gates said in court papers filed Thursday that he does not oppose their departure and that he has new counsel, Thomas C. Green.