For the first time in more than a decade, the sprawling House of Delegates district that extends from southwest Baltimore County through Howard County is in play.

With three long-serving incumbents retiring from District 12, a large field of competitors is hoping to pounce on a rare opportunity to win election in what is seen as a diverse and important district.

The wide-open race has attracted 13 candidates, including two physicians, a former speechwriter for Gov. Martin O'Malley and a former state lawmaker who is financing his campaign with $85,000 of his own money. It has also spawned an attack website, accusations of carpetbagging and state charges against one candidate.

Redistricting, which combined the more conservative Baltimore County part of the district with the more liberal voters of Howard County, has only added to the uncertainty — and the stakes.

"It's going to be a very historic thing for both counties," said state Sen. Edward Kasemeyer, a Howard County Democrat. They've not had this kind of a race for a long, long time. Politically, it will be fascinating how it comes out. Almost anybody could win."

The Republican field for District 12 is set. The winners of the Democratic primary on June 24 are to face Gordon Bull, Joseph D. Hooe and Rick Martel in November.

Kasemeyer and the retiring delegates — Democrats Elizabeth Bobo, James E. Malone Jr. and Steven J. DeBoy Sr. — are supporting Terri L. Hill, a Columbia doctor whose sister, Donna Hill Staton, was Howard County's first black judge.

Hill, 55, a plastic surgeon, is among 10 Democrats running for the three open seats. The Democrats hold similar positions on most issues, but each is putting in long hours, knocking on thousands of doors in the hope of gaining an edge.

Hill writes personal notes at each house she visits. It slows her down, she says, but she hopes that it makes more of a connection with voters.

"I was tired of standing on the sidelines complaining," she said.

Bobo says she is backing Hill because she's an "excellent candidate with a passion for justice."

Michael Gisriel, a former delegate and longtime lobbyist, lent $85,000 of his own money to his campaign.

Gisriel, 63, says the money, which he's used to purchase a billboard in Catonsville's business district, shows his commitment to the district. He says the four years he spent in the General Assembly from 1987 to 1991 make him the most experienced choice.

"This is the only district out of 47 in the state with no incumbents," he said. "I'm the only one in the field who's held elected office. I've worked in Annapolis for 30 years. ... Whoever else wins, I'll help the other two."

Gisriel, a former real estate columnist for The Baltimore Sun, was a licensed attorney from 1976 until 2009, when he was disbarred for depositing a $1,000 check belonging to former clients.

He blamed a "misunderstanding," and called the disbarment "excessive." He says he hopes voters will consider the sum of his experience. "It knocked me down, but I got myself up," Gisriel said. "I've got a lot more positives than negatives."

Gisriel is closely trailed in campaign financing by Hill and fellow Columbia physician Clarence Lam, who have $67,000 and $73,000 on hand, respectively.

Lam, a Johns Hopkins doctor and legislative aide to Baltimore County Del. Dan K. Morhaim, is campaigning on a Segway.

"I've personally knocked on over 10,000 doors," he said. "It's important to get a good pulse on the different issues and perspectives that cut across the entire district."

Lam, 33, says his experience with Morhaim sets him apart: "I know how bills are drafted and how to get them through the committee."