PARKLAND, Fla. — When Alyssa Alhadeff and Alaina Petty, both 14, died this year in a mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla., their grief-stricken parents publicly mourned their daughters and questioned politicians over what could be done to prevent another tragedy.

Then they entered the political arena themselves, launching campaigns for the elected body with the most power over their daughters’ education: the Broward County School Board.

On Tuesday, one of them, Lori Alhadeff, won her election to the board, promising to focus on security and hold accountable administrators she sees as responsible for failing to quickly adopt safety measures after the shooting, which left 17 students and educators dead on Feb. 14. The other parent, Ryan Petty, was trailing late into the night behind the incumbent, Donna Korn, who would need at least 50 percent of the vote to avoid a runoff.

“I’m so excited to honor my daughter, Alyssa, and the 16 other victims in the Parkland shooting, and to be able to be the voice of change,” Ms. Alhadeff, 43, said after her victory.