Former Montgomery county executive Doug Duncan, left, council member Phil Andrews and County Executive Isiah Leggett prepare for a Democratic candidates’ debate March 7 in Bethesda. (Sarah L. Voisin/The Washington Post)

The Democratic candidates for Montgomery county executive used their first televised debate Tuesday to touch on all the differences they’ve argued over in more than two dozen joint appearances off the air: spending, education, the Silver Spring Transit Center and who will bring home more money from Annapolis.

Incumbent Isiah Leggett, council member Phil Andrews and former county executive Doug Duncan, appearing on Channel 8’s “NewsTalk with Bruce DePuyt,” took turns attacking each other’s votes and decisions on budgets.

Leggett, seeking a third term in the June 24 primary, said he inherited an unsustainable budget from Duncan. County spending increased about 36 percent over Duncan’s last three years in office (2003-06), which left Montgomery in poor condition to deal with the recession, Leggett said.

“We had to make some painful, difficult decisions,” he added. Spending dropped sharply in his first term.

Duncan, who was preparing to run for governor during the period of double-digit spending increases, said the county’s thriving economy made it possible.

“We were able to do it because we had an economy that was doing well,” Duncan said, vowing that if elected, he will expand Montgomery’s tax base again by attracting new jobs.

Andrews (D-Gaithersburg-Rockville), who has made fiscal conservatism a centerpiece of his campaign message, pointed out that Leggett funded labor union contracts at the same generous level as Duncan until the recession hit.

DePuyt reminded Andrews that he had voted in favor of all of Duncan’s budgets. He also suggested that Andrews used fearmongering in his opposition to the ambulance service fee that Leggett pushed through the County Council in 2012.

At the time, Andrews argued that lives might be lost because residents would hesitate to call 911 and incur fees of between $300 and $800. The costs are picked up by insurers. Andrews said he still believes that the fee is bad public policy and that Leggett “didn’t respect voters” by reviving the issue after it had been rejected in a ballot proposition.

All three candidates pledged in their own way to address the gap in academic achievement separating white and minority public school students. Leggett emphasized an inside-outside approach, saying the county must ensure that money is available to maintain small class sizes and fund the best educational technology. But the gap must be attacked just as aggressively outside the classroom, he added, with more safety-net programs to prevent children from coming to school hungry or with emotional problems.

Andrews called for more attention to the “engagement gap” in schools, contending that students not on track for college need more options for career and technical training. Duncan offered no specific prescriptions but put the onus on the Montgomery Board of Education and Superintendent Joshua P. Starr to up their game. He said has seen “a lot of defensive comments” from Starr and the board but no new thinking.

Duncan and Andrews renewed their attacks on Leggett for the problem-plagued Silver Spring Transit Center, which is nearly three years behind schedule because of design and construction flaws.

“An absolute fiasco,” said Duncan, who called for the resignation of General Services Director David Dise, the lead county official overseeing the project.

“If David Dise isn’t responsible, then who is?” Duncan asked.

When DePuyt asked Leggett whether he might have used more “in your face” leadership to head off problems with the project, Leggett said his decision to halt work and hire an engineering firm for a forensic analysis of the building demonstrated his leadership.

Duncan challenged Leggett’s assertions that county taxpayers will not be on the hook for cost overruns, pointing out that Montgomery will have to front the additional money and recover the cost in the courts, an approach he called “sue and hope.”

Leggett responded by pointing out cost overages in some of Duncan’s signature projects, such as Strathmore Hall. Duncan countered that at least those buildings are safe and open to the public.

Andrews and Duncan both promised to be more aggressive with Annapolis in bringing more money to the county.

“We’re getting clobbered in Annapolis,” said Andrews, especially in the area of money for school construction. Both promised to unite the state delegation into a more effective presence in the General Assembly to leverage money. Leggett said he’s heard the same complaint for 30 years and that it isn’t that simple. Unifying the state delegation “doesn’t mean that magical things are going to happen.”