Arlington County Treasurer Francis X. O’Leary announced that he will retire Monday after 30 years in office, in expected preparation for a run for the County Board in 2015.

O’Leary, first elected in 1984 by a margin of 89 out of 34,000 votes but has been reelected without a challenger in the last two elections, said his chief deputy, Carla de la Pava, will be sworn in as interim treasurer until a special election is held to fill the post during the Nov. 4 general election.

“I have lowered Arlington’s tax delinquency rate from over 9 percent to its current level of less than four-tenths of 1 percent, with hundreds of millions of dollars in tax savings,” he told the Arlington County Democratic Committee on Wednesday night. “Our rate of return on investments is the highest in Northern Virginia and our accounts are balanced to the penny on a daily basis. Innumerable citizens write us regularly praising the quality service they have received from this office. And no customer waits more than a few minutes to be served.”

While O’Leary is credited with professionalizing a once indifferent and inefficient office that is tasked with collecting and disbursing the county’s revenues, he also periodically ran into disputes with fellow Democrats. Most recently, he joined a call for a voter referendum on the proposed Columbia Pike streetcar. The County Board rejected that request last month.

In 1977, he said he would no longer actively work for the local party because its leadership censured him over a racially provocative campaign mailing he sent during a heated primary campaign against an African American challenger.

If he runs against current board members J. Walter Tejada or Mary Hynes in the 2015 race, “I’m most interested in sending a message that it’s time to wake up and smell the coffee,” he said. “It’s time for new growth and change in the Democratic structure.”

O’Leary, who celebrated his 71st birthday Wednesday, said he was “sorely tempted” to keep working until February 2015, so he could claim the title of longest-serving elected official in the county, exceeding Harry K. Green, commissioner of revenue from 1923 to 1951, and David Bell, clerk of courts from 1977 to 2007.

“Tempting as that is, I decided that what you did while in office meant more than how long you did it. Besides, coming in right behind Dave Bell in any contest is no disgrace,” he said.