The most heated part of the first Alexandria mayoral debate Thursday night centered on an issue that all three Democratic candidates agreed upon: that the historic City Hall and Market Square plaza are not for sale.

Allison Silberberg, the vice mayor who is in her first term on the City Council, criticized Mayor William D. Euille for speculating to a weekly newspaper last summer that one way to address the estimated $56 million in repairs needed for the 144-year-old structure would be to sell it and move the seat of government west.

“I don’t think it’s funny, and it’s caused a lot of fear,” said Silberberg, 51, a writer who says her campaign is based on “thoughtful, appropriate development” and preservation of the city’s historic districts.

“This is the heart and soul of Old Town,” Silberberg said of the 19th-century building and plaza located directly across from historic Gadsby’s Tavern, which dates to revolutionary times. “The very founding of our country is connected to that spot. And if we don’t care about that, what do we care about?”

Euille, 64, running for his fifth term as mayor but facing primary opponents for the first time since 2003, asserted that he would not sell City Hall. He said his comments to the newspaper simply reflected that he is considering every option, just as any business or corporation would if faced with massive repair costs.

Kerry Donley, Allison Silberberg and William Euille speak to a crowd April 23 in their first joint appearance as they run for the the Democratic nomination for the Alexandria mayoral race. (Patricia Sullivan/THE WASHINGTON POST)

“No one has more connection to City Hall’s history than myself,” he said, noting that his office window looks out on Market Square, where slaves were sold. Euille is the city’s first African American mayor.

Kerry Donley, 59, a former mayor and council member who has been out of office for two years, agreed that it was “utter lunacy” for anyone to think that Alexandria would sell City Hall, a replica of an 1817 building that burned down and was rebuilt in 1871.

During the rest of the debate, held in the cafeteria of Douglas MacArthur Elementary School, the candidates vying for their party’s nomination sparred primarily over development, the city’s financial state and parking.

The two topics that drew the most audience responses were condemnations of the Department of Defense building at Interstate 395 and Seminary Road and the King Street bike lanes. The 100 or so West End residents despised both. In the past eight years, Donley noted, the city’s expenses have exceeded its revenues, and the burden of paying for the ongoing cost of government has fallen disproportionately on residential taxpayers. Over the past two years, because of increased assessments, the average residential taxpayer has seen an increase in the tax bill of $500, which Donley called unsustainable.

The city should focus its efforts on bringing in more businesses, which don’t demand as much in services as residents do, and building up the tax base, he said. Alexandria should be focused more on “smart growth” by centering development around transit hubs and investing more in its schools.

Euille defended his record and said a vote is set for May on where to put the Potomac Yard Metro stop, which is expected to lead to more business investment. Demands for more commercial development overlook the fact that there is vacant office space throughout the region, he said, and it will be 3 1 /2 years before it’s filled. According to regional projections, Alexandria could have an additional 50,000 residents by 2040.

Both he and Donley agreed that the city is facing a bill of several hundred million dollars to repair or replace some of its outdated sewers. It’s an issue many municipalities will have to address, Euille said, although Donley said city leaders should have acted earlier.

Silberberg said the city needs to be “very careful” about what it builds. “For the last 20 years, we’ve developed our way out of a budget crisis,” she said. “Just developing massively is not taking into account protecting our neighborhoods.”

Silberberg, who was the City Council candidate elected three years ago who was opposed to the city’s plan to redevelop the waterfront, said she was proud of her vote this month against a mixed-use development on the site of the Robinson Terminal South warehouse, because she thought the architectural design was wrong for the waterfront.

The Virginia Public Access Project , parsing state-required campaign-contribution requirements, reported Friday that Euille led the fundraising race in the first quarter with $95,629 in donations, followed by Donley with $40,203 and Silberberg at $21,345. The primary is June 9. Republicans have not announced whether they will field a candidate.

The next mayoral candidates’ debate will be held at 7 p.m. May 5 at Francis C. Hammond Middle School. A mayoral debate and 45th District candidates’ debate will be held at 7 p.m. June 2 at the George Washington Middle School.