SCARBOROUGH, Maine (AP) — Graham Platner said Wednesday that he plans to withdraw from the U.S. Senate race in Maine after facing an allegation of sexual assault, shuttering an insurgent campaign that had withstood months of controversy only to implode and imperil Democrats’ attempt to regain power in Washington.

Platner’s exit will most likely force a reckoning within the party, which has been divided between its moderate and progressive factions, when it is struggling to unify during this year’s midterm elections. Maine is considered a key state for control of the narrowly divided Senate, and Democrats were desperate for a candidate capable of defeating Republican Sen. Susan Collins while President Donald Trump is broadly unpopular.

In an 11-minute video posted to social media, Platner said the process to replace him needs to be “open, transparent and democratic” and to reflect the will and values of people who supported him.