Correction: Earlier versions of this article misstated the filing deadlines for Democratic candidates to replace Democrats Mary Hynes and J. Walter Tejada on the Arlington County Board. The filing deadline is March 26, not March 27. The article has been corrected.

Mary H. Hynes (D), right, with fellow Arlington County Board member Jay Fisette (D). (Tracy A. Woodward/The Washington Post)

Arlington County Board chairman Mary H. Hynes (D) will not run for another term this fall, creating a second opening on the five-member board after a tumultuous political year.

The departure of Hynes, 59, and fellow Democrat J. Walter Tejada in December could significantly shift the board’s priorities if either of their replacements forms an alliance with the board’s two fiscal skeptics, John Vihstadt (I) and Libby Garvey (D).

Vihstadt won his seat in a low-turnout special election in April, becoming the first non-Democrat elected to the board since 1999. He then won a full four-year term in November. Both of his campaigns centered on objections to large, expensive capital projects, including the now-canceled Columbia Pike streetcar.

Vihstadt often joins Garvey in questioning county spending priorities. The fifth board member, Jay Fisette (D), usually aligns himself with Hynes and Tejada.

During a county Democratic Party meeting Wednesday night, a crowd greeted Hynes with two standing ovations.

In her speech, she urged the group to band together and “collaborate, use common sense and build a consensus” to ensure that the party’s progressive values remain intact after she and Tejada leave office.

“Our party, our values and our people are responsible for creating the Arlington we know and love today, and don’t ever let anybody tell you different,” Hynes said, referring to complaints from political opponents that the county has lost its way.

Hynes had hinted before her Jan. 1 installation as chairman that she was considering retirement.

“It is time for a new chapter for me,’’ Hynes said. “As many of you know, I have a new grandchild in California who is hard to visit with the schedule I have.” She added that she is looking forward to reading for pleasure.

There have not been two open board seats in Arlington for more than 30 years, said voter registrar Lina Lindberg. The situation will probably prompt a lively Democratic primary in June and possible challenges by Republican or independent candidates seeking to build on the foothold created by Vihstadt’s arrival.

No candidates have formally declared their intentions to run. But Kip Malinosky, the chairman of the county’s Democratic committee, said he anticipates “five or six” to throw their hats into the ring, prompting a round of lively debates after the March 26 filing deadline.

The withdrawals of Hynes and Tejada, coupled with the anti-streetcar movement, “have been a real turning point,” Malinosky said. “This is becoming a really good question for the vision of Arlington and where we want to go from here, and that is definitely something that will be debated.”

In November, Hynes joined with then-chairman Fisette to abandon the long-planned Columbia Pike and Crystal City streetcar projects because of ongoing, vocal opposition. A number of other examples of civic skirmishes have broken out in the past two years — disagreements about school overcrowding, whether the county is devoting enough resources to affordable housing, whether residential development should trump parks and recreation centers, and whether the board is too friendly to developers who build big residential towers. 

Hynes said the disagreements did not influence her decision to retire. But she has often found herself trying to defend and protect the “Arlington Way,” a tradition of lengthy community discussions that seek consensus before major decisions.

“My two major issues have been civic engagement and our capital improvement program,” she said. She said she felt the 2014 capital improvement budget adequately addressed her concerns in that area, and she expressed hope that a recently launched community planning process would improve civic engagement.

Hynes said she has “no desire” to run for the Virginia General Assembly or other elected office. But she would not entirely rule out a future campaign.

She said she will remain engaged in civic life, including “how the field forms up” to succeed her, and may endorse board candidates. “I have some definite opinions,” Hynes said.