Labour, the Conservatives, the Liberal Democrats, the Greens and Restore Britain all said they will not contest the Clacton by-election Farage triggered by resigning and seeking an immediate return.
Farage cast the vote as a "people versus the establishment" fight, but rivals called it a distraction from a parliamentary standards investigation into an undeclared £5m gift and other financial support.
The inquiry by standards commissioner Daniel Greenberg has been paused during the vacancy, though it could resume if Farage regains the seat; a suspension could then trigger a recall petition if 10% of voters sign.
Reform wants the poll held as early as August and says it would cover a cost estimated at £228,964 in 2016, while Count Binface has confirmed he will run.
Separate scrutiny is also widening around Reform: Richard Tice says he asked the NCA to investigate a possible leak after reports flagged an £80,000 loan and a £1m donation linked to George Cottrell and his mother.