Julian Haffner of Gaithersburg, the current treasurer of the Montgomery County Democratic Central Committee, has decided to drop his bid for an at-large seat on the County Council and run instead for a newly open delegate seat in Gaithersburg/Rockville-based District 17.

His move is the latest development in the wake of the surprise announcement by Del. Andrew Platt two weeks ago that he had decided not to seek a second term in the Maryland General Assembly.

“While I am disappointed to learn of Delegate Platt’s decision not to seek re-election, his early retirement has created an opportunity that previously had not existed,” said Haffner, who in late November had announced he was joining the already crowded contest for County Council at-large.

His exit from that race narrows—to 28—the field of candidates seeking the nomination for four at-large nominations in the June 26 Democratic primary. At one point, the number of Democratic contenders in the council at-large race had reached 30.

“I am extremely excited about a run in District 17, where I have focused the majority of my community work as a member of the Democratic Central Committee,” Haffner, an attorney in the Bethesda-based law firm of Longman & Van Grack, said in a press release late Wednesday.

Haffner becomes the third non-incumbent candidate taking aim at the open seat created by Platt’s decision not to seek re-election. Another erstwhile contender for an at-large council seat, Montgomery County Board of Education member Rebecca Smondrowski, also has switched to the District 17 delegate race in the wake of Platt’s decision.

Two incumbent Democrats, Dels. Kumar Barve and Jim Gilchrist, are seeking re-election to the remaining two delegate slots in the district—and announced last week they had decided to add another non-incumbent contender, Rockville City Council member Julie Palakovich Carr, to their slate in the primary.

Besides his role as treasurer of the MCDCC, Haffner, 41, is vice president of the Association of Black Democrats of Montgomery County. He is married to Laurie-Anne Sayles, a former president of the association who this past November was elected to a seat on the Gaithersburg City Council.

In addition to his law practice, Haffner is co-founder and general counsel for the Mighty Mizizi Music Co., a firm that provides services for independent songwriters and publishers.

Palakovich Carr, first elected to the Rockville council in 2013, launched her campaign for delegate last July—preparing to take aim at the three incumbents who, until Platt’s withdrawal, had planned to slate together for re-election.

With Platt out, the decision by Barve and Gilchrist to slate with Palakovich Carr gives her not only the endorsement of the incumbents, but allows her to closely coordinate her efforts with them and to share the cost of campaigning.

In an interview last week, Barve cited Palakovich Carr’s science background as one reason he and Gilchrist had decided to slate with her: She holds a master’s degree in biology and works for the Washington, D.C.-based American Institute of Biological Sciences, a nonprofit organization that promotes policymaking grounded in science.

Barve also cited Palakovich Carr’s service on the Rockville council as a factor in the slating decision.

“She’s a municipal elected official, which is really important for District 17 because somewhere in the region of 95 percent of the constituents live in Rockville and Gaithersburg, and that perspective is really important,” Barve said of the two municipalities—the two largest cities in Montgomery County.

But the fact that Barve and Gilchrist, both Rockville residents, have chosen to slate with a Rockville council member has caused some grumbling within Gaithersburg political circles. Gaithersburg and Rockville, as the third and fourth largest cities in Maryland, are within several hundred residents of each other in population, according to the latest Census Bureau estimates.

Haffner and Smondrowski, both Gaithersburg residents, could seek to capitalize on this in the upcoming primary to replace Platt, also a Gaithersburg resident.

Barve has sought to respond to this issue by citing his long-time status as a Gaithersburg resident before relocating to Rockville in 2015. At the time, he was seeking the Democratic nomination from the 8th Congressional District; Rockville is largely in the 8th District, while most of Gaithersburg lies in the neighboring 6th Congressional District.

In an effort to defuse the residency issue in the upcoming primary, Barve noted in an email last week: “I have lived or worked in Gaithersburg from 1981 to 2015; 34 years, over half my lifetime … . So, I probably have more Gaithersburg time under my belt than most.”

No Republicans have yet filed to run in the 17th District, where Democrats enjoy a more than 3-1 edge in voter registration.