Howard Fischer/Capitol Media Services

Martha McSally answers questions on Dec. 18, 2018, on the heels of Arizona Gov. Doug Ducey appointing her to the U.S. Senate.

A long standing provision to the U.S. Constitution could place Arizona Sen. Martha McSally’s appointment in jeopardy.

An attorney for Libertarian Barry Hess and other politicians has asked a federal judge to order a statewide election — and soon —  to let voters choose who should sit in the state’s second U.S. Senate seat.

Gov. Doug Ducey first appointed Jon Kyl to fill the late John McCain’s seat, then appointed Martha McSally in January when Kyl quit.

Attorney Michael Persoon for Hess told the judge, the governor had no constitutional right to hold that seat until the 2020 election.

The law, he has argued, requires voters choose their own candidate within 100 days of the vacancy.

The governor’s attorney has countered with another interpretation, the law allows the administration to appoint a U.S. senator if vacated seat happened within 150 days of the next scheduled election, which it did.