Off-year, spring elections for municipal offices typically never draw much interest from younger voters.

But the May 3 election has another problem: It is an all-mail ballot.

And that is even more of an anathema to voters between the ages of 18 and 24, who are often more transient and less likely to have a permanent address than older voters.

“Older people own houses and have land lines,” said Debbie Willhite, general consultant for Carol Boigon’s mayoral campaign. “Younger people don’t get what the U.S. mail is all about. They do everything online.”

Today is the final day to register to vote for this spring’s election for all 13 City Council positions, the mayor, the clerk and recorder and the auditor. Voters can register at www.govotecolorado.com.

Eighteen- to 25-year-olds make up about 8 percent of Denver’s roughly 432,000 registered voters. (The number of active voters is 221,252, according to the secretary of state.)

In the 2003 Denver municipal election, about 5 percent of voters who cast ballots were between 18 and 28. In 2007, 3.5 percent were in that group.

“Most campaigns are not going to have the resources or the national machine to chase ballots,” said Berrick Abramson, campaign manager for mayoral candidate James Mejia. “It’s going to be the historically active seniors and older voters that they will go after.”

New Era Colorado, a nonprofit focused on boosting young-voter turnout, is busy registering voters, educating them about the issues and even produced an MTV-inspired video that visits six of the mayoral candidates’ “cribs.”

On Wednesday, the group hosts “Candidate Survivor” at Casselman’s Bar and Venue, a mayoral forum in which audience members will text votes for a “winner.”

“If a young voter is left to be on their own and no one is courting them, they won’t engage,” said Steve Fenberg, New Era Colorado’s executive director. “If they court them, they do turn out. The payout is big.”

Most mayoral candidates have websites, Twitter accounts and Facebook pages, and a few have purchased Internet advertising. But most outreach is still TV ads and calling homes during the day and going door-to-door before sundown, reaching the older and active voters.

“It’s a real challenge to go after the under-30-year-old voters in any sort of targeted and practical way,” said Willhite, from Boigon’s campaign.

One-third of mail voters tend to return the ballots within the first week of ballots’ arrival in mid-April. The next third come in over the following weeks. And the final third are delivered within the last 72 hours, said Floyd Ciruli, political analyst.

The number of active voters in Denver has fallen by more than 100,000 people since 2008, posing another problem, Ciruli said.

“The rolls are very small, and there isn’t a particular candidate with a theme that resonates with younger voters,” he said. “This is an election all about austerity, not about a new vision and an exciting change of life. That is not appealing to a young voter.”

Jeremy P. Meyer: 303-954-1367 or jpmeyer@denverpost.com