James Comey, the FBI director who was fired last year by US President Donald Trump, is urging voters to support Democrats in November's midterm elections.
Comey said on Twitter that the "Republican Congress has proven incapable of fulfilling the Founders' design that 'Ambition must counteract ambition."'
That refers to the need for Congress to provide checks and balances to presidential power.
Comey wrote: "All who believe in this country's values must vote for Democrats this fall. History has its eyes on us."
The former FBI director recently said he no longer considers himself a Republican.
On Monday, after Trump's press conference with Russian President Vladimir Putin, Comey tweeted, "This was the day an American president stood on foreign soil next to a murderous lying thug and refused to back his own country."
Australian Associated Press
