The Federal Election Commission said Tuesday night that it identified the issue affecting its electronic filing system and was implementing a fix, after reports that a hacker or hackers had targeted the agency's systems days before the midterm elections.
But the system remained offline early Wednesday, cutting off a key window into campaign money just as late-election spending surges.
An FEC electronic filings official told campaign compliance firms Monday night that a "bad actor" was attempting to breach the agency's systems and that public-facing services had been shut down, according to an email obtained by Reuters. The filing system has been offline since around 10 p.m. ET Monday.
The FEC has not said who was behind the reported breach attempt, whether anyone gained access to its systems or whether any data was compromised. Previously filed reports remain searchable.
The FEC told CNBC that the agency's IT staff is working to restore the service.