For a special election, especially one occurring via mail-in ballots amid a pandemic, some things went surprisingly well in last month’s 7th Congressional District vote. Overall turnout was relatively strong at about 32%, compared to just 8% the last time a special election was held for that position — in 1996, when Elijah Cummings was running to take over the seat, which at the time had been vacated by Kweisi Mfume, instead of the other way around. And fewer than 1% of people voted in person (1,009 to be exact; five of them so they could take advantage of same-day registration) out of the 157,075 voters whose ballots had been counted as of Tuesday afternoon.

Those factors appear to bode well for next month’s statewide primary election, both in terms of participation and coronavirus containment. But a deeper look at preliminary data from District 7, which covers parts of Baltimore City and Baltimore and Howard counties, reveals areas of concern that need addressing to ensure most of those who want to vote can.

Of the ballots sent out to the district’s nearly half a million eligible voters, at least 28,608 never made it to their intended recipients, largely because the addresses on file were out of date, according to hand counts of returned ballots performed by the three local elections boards in the district. (The State Board of Elections asked for the counts after learning through inquiries from us that the U.S. Postal Service data they were relying on was way off, both in the number of returned ballots and their supposed destinations.)

In the city alone, more than 20,000 ballots were returned as undeliverable; that’s nearly 10% of the eligible voters registered in Baltimore. Some of them may have moved out of the district, of course, but many are likely just in a new place nearby, and because they didn’t update their address with the elections board, they never got a chance to cast a ballot — at least not from a safe, social distance.

That’s of particular concern, given that the city is already in an underdog position when it comes to elections held by mail. A 2011 study sponsored by the Pew Charitable Trusts found that urban voters are 50% less likely to vote in a mandatory mail election, and the participation numbers seen here seem to bear that out. In the special election, turnout in Baltimore City was far lower than the counties: 25% compared with 38%. It was also low for the primary on Feb. 4 — way back in pre-pandemic times, when in-person voting was the norm — but the difference was less pronounced: 19% of eligible city voters cast a ballot then, compared with 23% for Baltimore County and 25% for Howard.

The good news is that the same Pew study also found that outreach (at least four separate communications) can overcome some of the negative effects of mandatory mail-in voting for urban voters. And this week, the State Board of Elections launched a $1.1 million education campaign aimed at getting the word out about how, when and where to vote. Elections officials plan to target radio, TV, online news, and social media sites with advertising and information through the effort, which is roughly 30 times larger than the $37,000 initiative undertaken for the 7th District special election.

The bad news is that there’s very little that can be done now to deal with the address issue. The ballots for the June 2 primary have already gone out (Baltimore City’s were mailed Friday).

“It’s a problem,” Nikki Charlson, deputy administrator for the State Board of Elections, acknowledged.

In states where vote-by-mail is frequently used, elections boards will proactively send out interim mailings to try to find the bad addresses before ballots go out, but there wasn’t time to do that here. And so, if primary ballots come back to local elections boards, workers there will try to update the addresses and send out new ballots before June 2, but they only have so much capacity to do that. And if ballots come back at the same rate as they did in the city in the 7th District race — forget about it. So many came back then, that mail carriers would bring them to the Baltimore City Board of Elections in trays, 10 to 15 at a time, said Baltimore Elections Director Armstead B.C. Jones Sr.

If your address is wrong in the system, you can take action on your own to correct it and request a new ballot; the sooner the better. If you’re not sure, you can look it up and make any necessary changes here: voterservices.elections.maryland.gov/VoterSearch or by calling 410-269-2840.

There are also a few things voters who do receive their ballots can do to ensure each is counted. First, send it back on time — postmarked by June 2. More than 1,500 Baltimore City ballots in the 7th District special election were returned too late, according to Mr. Jones. (Note to those without a flag to raise on your mailbox: You can still leave outgoing mail there; your letter carrier will pick it up.)

Don’t forget to sign and date the oath on the envelope (at least 124 people didn’t do that in the city); don’t worry about postage (none is required); and don’t fail to update your address because you don’t want to be called for jury duty in the city (it happens, Mr. Jones said).

The elections boards have made some mistakes too, notably by putting the wrong date on the primary ballots (they read April 28, which was the date Maryland had originally planned to hold the primary, before coronavirus disrupted daily life) and by accidentally sending a segment of voters in Prince George’s County directions in Spanish only.

Linda Lamone, administrator for the State Board of Elections, says she and her staff and members of the local elections boards are talking nearly every day to “figure out how to do things” and learn from the 7th District results. They’ve also reached out to other states for their best practices.

Given the stakes — our very democracy — we certainly hope they’re doing every last thing they can think of.

The Baltimore Sun editorial board — made up of Opinion Editor Tricia Bishop, Deputy Editor Andrea K. McDaniels and writer Peter Jensen — offers opinions and analysis on news and issues relevant to readers. It is separate from the newsroom.