The U.S. Postal Service overhauled its organizational structure as Democrats called for an investigation into whether the changes implemented by President Donald Trump’s postmaster general pose a threat to mail-in ballots for the November election.

Postmaster General Louis DeJoy on Friday said the new structure, organized around three business units, will increase efficiency by reducing costs and boosting revenue.

The announcement prompted criticism from Democrats, who have already raised alarms over mail delays that they worry will skew the election results if ballots aren’t returned in time. At stake are votes in 34 states — including almost all of the presidential battlegrounds — that won’t count mail-in ballots unless they are received on or before Election Day, even if the ballots are mailed on time and subject to Postal Service slowdowns.