Republican U.S. Rep. Bruce Poliquin is challenging the constitutionality of Maine’s ranked-choice voting system used for the first time in congressional races in Maine.

Judge Lance Walker declined Thursday to stop the process.

Final tabulations are expected around Thursday afternoon in the race between Poliquin and Democrat Jared Golden.

Poliquin, who had an edge in first-round votes, said he has a duty to challenge the new voting system on constitutional grounds. Voters approved it in 2016.

The lawsuit remains alive because Walker didn’t rule Thursday on the constitutionality of the system.