Read: The most important states already have vote by mail

States with upcoming primaries this year should convert them into vote-by-mail elections. Even with Bernie Sanders’s withdrawal from the Democratic presidential race, many important state and local primary contests are yet to be decided. Every state should adopt the system before the November general election. Wisconsin’s experience should not be repeated.

In Oregon, where I live, vote by mail has been the sole method by which elections have been conducted since 2000. All registered voters are sent a ballot approximately three weeks before Election Day. If a voter no longer lives at the address on record, the ballot is not forwarded. After marking the ballot, the voter puts the ballot in a secrecy envelope, which contains no identifying information. The secrecy envelope is then placed into a second mailing envelope. Voters are required to sign the outside of this mailing envelope, which they then mail or take to one of the numerous drop-off sites in the area. (In a further convenience for voters, Oregon has recently moved to prepaid postage for these mailing envelopes.) When the ballots arrive at the local county-elections division, the outside signature is compared with the original registration signature on record at the office, to protect against fraud.

These safeguards are robust. As it happens, my two children—then college-age—have twice made an error on their mailing envelope (they signed each other’s mailing envelope or used an illegible scrawl instead of the original registration signature). In both cases, the county elections division caught these errors, contacted them to rectify the problem, and my children were still able to vote.

The introduction of vote by mail in Oregon has been gradual. In 1987, the legislature made vote by mail an option for local and special elections, and a majority of counties then adopted vote by mail for local elections because the administrative costs were lower than operating polling stations. In 1993, vote by mail was used for the first time in statewide ballot measures.

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In 1995, the Republican-controlled state legislature passed a bill that would have adopted vote by mail for all types of elections. The impetus was the high level of absentee voting (22 percent) in the 1994 general election, which had delayed the certification of certain races for many weeks, including a close U.S. House seat. The reason for this delay in 1994 was that in so-called hybrid elections, officials needed to make sure that no one voted both at the polls and by absentee ballot. This was a rare and unlikely occurrence, but in a close election, this possibility had to be examined.

John Kitzhaber, Oregon’s Democratic governor, vetoed the vote-by-mail bill, arguing that it was too early for Oregon to adopt such a drastic electoral reform without further study. The opportunity for further experimentation soon arrived when Senator Bob Packwood resigned. The December 1995 primary and the January 1996 general election to fill his seat were conducted by mail. Turnout was high. The Oregon League of Women Voters led a successful petition drive to put a vote-by-mail measure on the 1998 general-election ballot. This ballot measure passed, winning 67 percent of the vote.