When Democrat Libby Garvey, Republican Mark Kelly and their Green Party opponent Audrey Clement have taken their places at Arlington County candidates’ forums in the past eight weeks, they look out on an audience that rarely fills the seats available.

Arlington is holding a special election Tuesday for a County Board seat left vacant after Barbara A. Favola (D) was elected last year to the Virginia Senate. The job will last only eight months before it’s up again, so that might account for the sparse turnout at forums. But whoever wins Tuesday could have an immediate impact on next year’s budget.

All three candidates have expressed skepticism over large, expensive development projects in the works, such as the $250 million Columbia Pike streetcar and a $50 million Long Bridge Park aquatic and fitness center. Kelly and Clement have raised questions about the ongoing costs for the Artisphere, the Rosslyn arts space, and the recent approval of an unadorned, experimental black box theater in Virginia Square.

Garvey is pushing for cost-benefit analyses of the projects, part of her pitch for a more systematic approach to county priorities, and has floated the idea of a voter referendum on the streetcar. Kelly, who wants to hire an independent inspector general and require immediate disclosure of county spending, says that he has not found support for the trolley along the pike and that it’s time for prominent backers such as board member Chris Zimmerman to admit the idea is a mistake.

Clement, who called the trolley a “gimmick” to induce more development, advocates improved bus service and new articulated or double-decker buses, which would cost one-quarter of the price of a trolley and would not tear up the street for years.

The three are trying to crack the hegemony of an all-Democratic board that some have called arrogant and unresponsive to residents and neighborhood activists, despite recent efforts by Chair Mary H. Hynes to encourage civic engagement by holding “Open Door Mondays” for one-on-one meetings with residents, and setting up Participation, Leadership and Civic Engagement (PLACE) training sessions.

Even Garvey, the Democratic candidate and a 15-year veteran of the county School Board, argues that she is an independent and in some ways an outsider, winning the nomination of her party without the support of the incumbents.

Both Clement, a national leader of the left-leaning Green Party, and Kelly, deputy chief of staff for Rep. Tim Huelskamp (R-Kan.), have found surprising agreement on several local issues, although not larger national or philosophical issues.

“Do not present me with a budget that contemplates a tax-rate increase when assessments are going up,” said Clement, describing the guidance that she would give the county manager next year. “Number two, I want a budget that prioritizes needs over wants.”

“In the last decade, property-tax bills doubled while inflation was up 25 percent and wages went up 40 percent,” Kelly said. “We don’t need to fund every project that sounds like a good idea. . . . The key to improving the long-term quality of life is to focus on core services now.”

Their priorities, as expressed at candidates’ forums, on their Web sites and in interviews, also sound similar. Kelly focuses on fiscal discipline, public safety, schools, water and sewer, trash pickup, road improvements and a “non-negotiable” commitment to Metro. “We shouldn’t hire 37 new people,” he said. “And I wouldn’t buy 2020 14th Street,” a commercial complex that the county plans to use for government offices and a comprehensive homeless services center and shelter.

Clement argues for improving those same basic services, particularly the “deplorable condition” of the streets, as well as returning libraries to seven-day-per-week operation and restoring budget cuts in services for youths, people with disabilities and the elderly. She also objects to the cost of the purchase and renovation of the 14th Street building, which she characterizes as “breaking the county budget.”

Garvey is leaning on her background as an elected official. “I know how to do this job,” she says as part of her stump speech. Setting policy for schools, she said, isn’t that different from the job of the County Board, particularly if one focuses on setting clear goals and priorities, hiring managers such as superintendents and working with others.

Her priorities, beyond installing a strategic plan, include infrastructure maintenance, public safety, improving the county’s green space and the safety net for its most vulnerable residents. She also promises to ask questions about whether the county is holding too much money in its various reserve funds.

As the leader in fundraising and a member of the political party that dominates Arlington politics, Garvey is the consensus front-runner. While she worries about Democratic voter assumptions that lead to low turnout — which she termed “an uphill battle for our democracy” — her opposition actively agitates for breaking up the Democratic unanimity on the five-member board.

“There’s one thing citizens can do to arrest the arrogance of the County Board — elect a non-Democrat,” Clement said.

“We need to think about changing course,” Kelly said. “The only way [the County Board] is going to change is if you tell them they could lose.”