In this age of social media, a growing number of Maryland lawmakers have taken to Twitter to communicate with constituents and court voters for their next election.

Only about half of those with accounts, however, are following a state regulation that requires candidates to include information about their campaigns on their profiles.

Under regulations issued in 2010, all candidates in Maryland are supposed to include an “authority line” when they promote themselves on social media, including Facebook and Twitter. Violations are subject to a fine of up to $500.

The Washington Post identified 92 Twitter accounts maintained by the state’s 188 senators and delegates. Of those, only 45 included authority lines that identify the name of the campaign entity and its treasurer.

Among those who hadn’t included the information prior to being contacted by The Post was Del. Jon S. Cardin (D-Baltimore County), who chairs a House subcommittee on election law.

On Twitter, Cardin identifies himself as a “husband, father, delegate and candidate for attorney general of Maryland,” and he provides a link to the Web site for his 2014 bid for statewide office.

He added the authority line Thursday, after The Post inquired about why he didn’t have one.

“It’s an oversight that we have since fixed,” Cardin said in an interview. “We all make mistakes, and the question of character is how you handle that.”

He added that his Twitter account started out as a personal account before it included campaign material.

Three other state lawmakers running for attorney general — Sen. Brian E. Frosh (D-Montgomery) and Dels. Aisha N. Braveboy (D-Prince George’s) and C. William Frick (D-Montgomery) — provide authority lines on their Twitter accounts.

State elections officials say that state lawmakers don’t need to explicitly mention their campaign to trigger the requirement that they include an authority line.

Promoting their views, their votes and their events are all considered activities that enhance the reelection prospects of elected officials and are considered campaign activity, said Jared DeMarinis, director of the Maryland State Board of Election’s candidacy and campaign finance division.

The authority line is meant to signal to voters that Twitter accounts of candidates are authentic, DeMarinis said, and it’s in the best interest of candidates to comply with the regulation for that reason alone.

With new enforcement powers that were included in legislation passed this year, DeMarinis said the elections board intends to start cracking down on candidates who aren’t following the rules.

A reminder about the social-media requirements was included in a memo that the board sent in September to candidates, their chairman and their treasurers. There are also reminders on the board’s campaign finance Web site.

Del. Justin D. Ready (R-Carroll), one of the more prolific tweeters in the House, said it was “easy enough” to add an authority line to his Twitter account when the regulation was issued in 2010.

“I try to be on top of all the rules,” said Ready, who’s been on Twitter since 2009. “I’m sure in most cases, where people haven’t done it, it’s not an intent to do anything wrong.”

Ready’s tweets include pictures of him at events and links to news stories in which he’s mentioned.

“It does help you stay in touch with people,” he said.