ST. PAUL (AP) — A Republican state representative and a GOP activist are challenging an agreement to accept mail-in ballots in Minnesota that arrive up to a week after the November election, adding to the nationwide legal fight over voting rules before the presidential election.

Rep. Eric Lucero and Ramsey County activist James Carson, who both participate in the Electoral College, filed the lawsuit Tuesday in U.S. District Court. The lawsuit states the agreement by Secretary of State Steve Simon, a Democrat, violates federal law establishing Nov. 3 as the date of the 2020 election.

Simon agreed to extend the deadline because of a legal challenge by groups who sought to allay concerns about voter safety during the coronavirus pandemic and ease mail-in voting requirements. State election officials agreed to accept mail-in ballots arriving a week late, even if they don’t have a postmark, the Star Tribune reported.

The Republicans’ lawsuit said the agreement violates the constitutional requirement that Congress sets the times of presidential elections and that state legislatures set the manner.

“This agreement threatens the integrity of the upcoming election, will result in widespread and severe vote dilution, will (at a minimum) create substantial uncertainty and delay over Minnesota’s ability to certify its results,” the lawsuit said.