The cost of the Columbia Pike streetcar has risen to $358 million, Arlington County officials said Tuesday, up more than $100 million from their previous estimate and $48 million above what federal transportation officials projected last year.

Controversy over the project has been fueling a groundswell of electoral unrest in Arlington, where voters last month elected a non-Democrat to the County Board for the first time in 15 years.

The successful candidate, John Vihstadt, a Republican who ran as an independent, had criticized the streetcar on the campaign trail. Now the Democrat he beat, Alan Howze, has joined Virginia state Del. Patrick Hope (D) in calling for a voter referendum on whether the project — which officials say will spur additional development in the Columbia Pike area — should go forward.

The proposed streetcar would run 4.5 miles from the Skyline area of Fairfax County along Columbia Pike to the Pentagon City Metro, and then skip over to the Crystal City Metro stop, where local officials hope to connect it with another streetcar line running down U.S. Route 1.

Dennis Leach, deputy director of transportation and environmental services, told the Arlington County Board on Tuesday that the Columbia Pike streetcar was essential to Arlington’s long-term competitiveness and economic development.

Right now, 24,700 people ride buses daily in the Columbia Pike and Crystal City corridors. But in 30 years, demographic projections say 60,000 people will be trying to commute and travel in those areas. The population of this part of south Arlington is expected to double, and a county-sponsored return-on-investment study of the streetcar said it would bring $3.2 billion to $4.4 billion in new development as well as 6,600 new jobs.

County Manager Barbara Donnellan told board members that the streetcar was a “generational investment.”

“We have not shied away from major investments in the past,” she said. “Every generation is asked to make decisions that benefit generations to follow. Building high-capacity rail in south Arlington . . . will allow us to grow fiscally and developmentally for years to come.”

Opponents of the streetcar project say they want a cheaper, rapid-bus system that could be built more quickly and would be more flexible.

In explaining the cost increases, Leach said he started with the U.S. Department of Transportation’s “extremely conservative” estimate from last year, which said the streetcar would cost $310 million — $60 million more than the county’s original projection. He added extra money to cover a larger contingency fund, a higher rate of inflation, higher engineering and start-up costs, and a proposed change in the size of the streetcars.

County officials said the cost of the proposed Crystal City streetcar project has grown substantially as well — from $146 million to $227 million. Officials cited the same adjustments made for the Columbia Pike project in explaining the increase. The Crystal City project has not attracted the same opposition as the Columbia Pike project, however, perhaps because area businesses have agreed to fund it through a set-aside tax.

Arlington County would be responsible for $287 million of the Columbia Pike streetcar costs, and Fairfax County would pick up the remaining $71 million, according to the plan presented Tuesday.

Arlington’s portion includes $140.5 million that officials hope to secure in federal funding; $70.7 million in state money; $12.3 million in regional transportation funding coming from Virginia’s new transportation tax; $18.3 million in transportation capital funds, provided by commercial property owners; $35.4 million in transportation capital bond funds; and $9.5 million set aside earlier for the streetcar.

Tuesday’s presentation came as part of Donnellan’s recommendation on Arlington’s 10-year capital improvements budget. The board will study the proposals and decide by July whether to accept, reject or alter the budget. Board Chairman Jay Fisette said a public hearing will be set in June.