Donald Trump’s campaign failed to produce any evidence of vote-by-mail fraud in Pennsylvania after a federal judge ordered it do so, according to a 524-page court filing obtained by the Guardian.

The order came from US district judge Nicholas Ranjan, a Trump appointee, earlier this month amid a lawsuit in Pennsylvania over several voting policies. The Trump campaign is suing to block the widespread use of official ballot dropboxes in the state in locations other than an election office, and to allow poll watchers to work in counties other than the ones they live in…

The campaign also offered no evidence of fraud specifically linked to dropboxes or mail-in ballots. The filing was first reported by Type Investigations. Several studies and investigations have shown that voter fraud is extremely rare.