HARRISBURG — Pennsylvania’s top elections official is warning that failing to replace voting machines by 2020 could make the state the only one without a voter-verifiable paper trail.

Kathy Boockvar, Pennsylvania’s acting state secretary, also told state senators Wednesday that election-security experts agree that moving to voting machines that allow voters to double check how their vote was recorded needs to happen by next year.

Boockvar was responding to questions from state Sen. Bob Mensch over why Pennsylvania is rushing to buy machines when there’s no example of a voter irregularity.