The U.S. Postal Service’s internal watchdog is investigating cost cutting that has slowed delivery and alarmed lawmakers ahead of a presidential election when up to half of U.S. voters could cast ballots by mail, a congressional aide said on Friday.

The Postal Service’s inspector general also will examine possible conflicts of interest involving new Postmaster General Louis DeJoy, who has donated $2.7 million to President Donald Trump and his fellow Republicans, according to Saloni Sharma, a spokeswoman for Democratic Senator Elizabeth Warren, who requested the investigation.

DeJoy owns millions of dollars in stock in Postal Service rivals and customers, according to a financial disclosure form filed by his wife.