A socially isolated election was held last week, and although it’s never wise to draw big conclusions from one-off events, the clear lesson in the race for California’s 25th Congressional District is this: It is time for Republicans to get on the vote-by-mail train.

The race in Southern California suggests that voting by mail can help Republicans win. So why are so many Republicans, including President Donald Trump, against it?

The special election suggests a different path. Yes, it was probably inevitable that Republican Mike Garcia would fare better than Democrat state Assemblywoman Christy Smith in the race to fill the seat vacated by Democrat Katie Hill, who stepped down from her House seat last fall. Yes, Republicans always hold an advantage in low-turnout special elections. And yes, the 25th had been in a safe GOP seat since 1993, until Hill came along in 2018 to pry it loose.

The 25th District sprawls through the chaparral canyon communities north of the San Fernando Valley and then east to the high-desert cities of Palmdale and Lancaster. It’s here that the lusher oases of Los Angeles County give way to the dry and gritty Central Valley. Lancaster and Palmdale are bedroom communities for Edwards Air Force Base, the realm of legendary test pilots such as Chuck Yeager and their experimental aircraft. Years ago, it was the kind of place that made California solidly Republican in presidential elections.

But it is there — in a state no longer so friendly to the GOP — that the Republicans just won a vote-by-mail slugfest. Some background: In March, Gov. Gavin Newsom, a Democrat, signed an executive order providing for mail-in voting, in part to avoid coronavirus spreading at polling places. Each of the 25th District’s 425,000 voters received a mail-in ballot before Tuesday’s election. These came with prepaid envelopes, and voters were able drop off ballots at collection centers in the district.

In the end, turnout wasn’t high — approximately 180,000 people voted. But while registered Democrats outnumber registered Republicans in the district, by Election Day 10,000 more Republicans than Democrats had returned their ballots by mail. With help from independents, Garcia is beating Smith by more than 17,000 votes, with a smattering of Election Day ballots still to be counted.

Why? Demographics. Older voters are the GOP’s most reliable base and comfortable with the U.S. Postal Service. Many seniors have been voting by mail for years, and this year, with everyone older than 60 falling into the high-risk category for COVID-19, they were inclined to stay home and mail in their ballots.

By contrast, most Americans ages 18 to 34 don’t “get the mail” on a daily basis. Their bills more likely come via email, and they pay them electronically. Many don’t own stamps. They don’t send letters. They don’t have subscriptions to magazines; their content is online. Compared with boomers, as a USPS inspector general found in 2018, they are almost half as likely to check their mail each day.

And yet, amid this almost perfect dry run for the fall election, the GOP is afraid of vote-by-mail?

Why? In part, because Trump has latched on to a conspiracy theory called “ballot harvesting” to explain Republicans’ loss of the House of Representatives in 2018. He tweeted as recently as last month that the practice is “rampant with fraud.”

California law allows ballots to be collected from voters and returned to state officials by a third party, as long as consent is given by signature on the envelope containing the ballot. This has led Republicans to claim that Democrats are harvesting ballots — collecting ballots from voters — so they can tamper with the contents. The practice does take place, but like most Trump allegations, the allegations of fraud aren’t backed up by evidence. On conservative talk radio, of course, it is taken as gospel.

Instead of complaining about ballot harvesting, it’s time for GOP campaigns to get in the game. Encourage their base voters to mail in their ballots. Help them do it when they cannot. Because GOP voters are more likely than Democratic voters to have saved a ballot while sorting their mail, they are more likely to have it available to be “harvested.”

The special election in California suggests that Republicans should be enthusiastic about voting by mail in November. It will help them ensure that their base votes, while keeping all voters safe. And remember: Trump himself voted by mail this year.

Rob Stutzman is a Republican political consultant in Sacramento, Calif. He wrote this for The Washington Post.