A few weeks ago, electric-car enthusiasts in the Senate were optimistic about quick passage of a measure that would designate permanent parking spaces near outlets in Senate garages for recharging electric vehicles.

But concerns about costs, and perhaps a misunderstanding about what the bill would do, have slowed its momentum.

Sen. John McCain’s (R-Ariz.) refusal to allow the bill to be brought to the floor by unanimous consent has complicated prospects for the measure.

“Sen. McCain objected to passing the measure by unanimous consent because there’s no demonstrated need for spending thousands of dollars to install electric car charging stations,” McCain spokesman Brian Rogers said. “This is an expensive perk for Senators not enjoyed by average Americans.

“If the measure is such a priority, the Majority Leader can schedule floor time on it whenever he sees fit, allowing the Senate to debate and vote on it in the light of day,” Rogers said.

Sens. Carl Levin (D-Mich.), Lamar Alexander (R-Tenn.) and Charles Schumer (D-N.Y.) are the chief advocates of the bill that would direct the Architect of the Capitol to set aside parking spaces close to outlets for lawmaker- and employee-owned electric cars.

They tried without success to move the legislation via a unanimous consent agreement on the eve of the Senate’s adjournment for Easter recess.

At the time, aides for all three Senators characterized Republican objections as based on the notion that the bill would be costly. Anyone who charges his electric car on Senate property would have to pay a monthly fee that would likely exceed what it would actually cost to recharge an electric car battery, an Alexander aide said.

The bill’s advocates originally wanted to install recharging stations. But in the year since the bill was introduced, stakeholders have shifted to a cheaper alternative: designate parking spaces near electrical outlets, allowing electric car owners to supply their own extensions and plug in their cars.

Continued dialogue with concerned lawmakers, they suggested, would assuage opposition.

“Let me talk with Sen. McCain,” Alexander said Wednesday afternoon. He could not elaborate on how he would proceed with attempts to advance the bill but reiterated that “it’s a fairly simple housekeeping bill that establishes a way to make sure that owners of electric vehicles can plug their cars in while making sure it doesn’t cost taxpayers any money.”

But even knowing that the bill wouldn’t mandate the purchase and installation of charging stations, McCain would not change his position to allow the bill to be passed without a recorded vote, Rogers said.

Bringing bills to the floor by unanimous consent is an effective way of moving noncontroversial bills through the pipeline. Bills that deal with the administrative side of Congress are generally not given a high priority and are rarely given much time for debate on the floor.

“It’s a shame Republicans continue to obstruct common-sense measures like this one,” said Adam Jentleson, spokesman for Senate Majority Leader Harry Reid (Nev). He would not comment on the possibility of making time for a floor debate on the bill.

Levin, in a brief interview with Roll Call last week, seemed resigned to the reality of the situation.

“I mean, it’s a bill that has no cost to government,” Levin said. “So if it gets cleared, it’s fine. If not, so be it.”

The American Public Gas Association and Natural Gas Vehicles for America have also weighed in, telling Roll Call that the measure sends a message that Congress favors one fuel source over another.

While they would prefer to see the bill go down, the groups have indicated that they have bigger fish to fry.

“The industry is not going to be made or broken by whether or not the Capitol favors natural gas vehicles,” NGVA President Richard Kolodziej said.