Igor Fruman and Lev Parnas, two Soviet-born associates of Rudy Giuliani, are charged with funneling $325,000 in foreign money into a super-PAC supporting President Donald Trump’s 2020 re-election campaign. Their indictment should serve as a warning about the threat of foreign manipulation of U.S. elections. It also proves the need for a functioning Federal Election Commission.

After a resignation in August, the six-seat commission is down to only three members. The commission needs four for a quorum and requires a quorum to authorize investigations by its office of general counsel. So FEC lawyers can work on cases previously authorized, but they can’t investigate new ones until the president nominates, and the Senate confirms, at least one new commissioner.

Trump has nominated Texas lawyer James “Trey” Trainor III — but Senate Majority Leader Mitch McConnell, who has fast-tracked dozens of federal court nominees, has dragged his feet on this one, failing to schedule a hearing or a vote. McConnell’s antipathy to campaign regulation appears to be trumping his duty to voters.

The FEC has never been an especially vigilant cop, but its work is still valuable. In addition to facilitating disclosure of campaign contributions and disbursements, it’s a venue for outside complaints. The criminal case against Fruman and Parnas may have originated in a complaint filed with the FEC last year by the Campaign Legal Center, a nonprofit group that supports campaign-finance regulation. The criminal charges filed by the Justice Department against Fruman and Parnas include lying to the FEC.

America’s elections are under attack. The Senate Intelligence Committee’s bipartisan report and the findings of special counsel Robert Mueller made that clear. Leaving the FEC impotent in the face of such threats is grossly irresponsible.

FROM AN EDITORIAL ON BLOOMBERG OPINION