RICHMOND -- Gov. Bob McDonnell's plan to abolish the gas tax and hike the sales tax to pay for badly needed roads faces stiff headwinds in a General Assembly that perennially makes transportation funding a top priority but fails to do anything about it.

Democratic leadership opposes the Republican governor's proposed roads plan, which McDonnell said would raise $3.1 billion over the next five years in part by raising the sales tax from 5 cents to 5.8 cents and eliminating the 17.5 cents-a-gallon tax on gas.

Sen. Janet Howell, D-Reston, said Senate Democrats would support raising the sales tax, but not eliminating the gas tax because it's a user fee. Democrats also insist that a portion of the new revenue goes to education.

Under Senate rules, McDonnell's plan needs only a simple majority, 21 of the Senate's 40 votes, to pass, but because the chamber is evenly divided between Republicans and Democrats, he'll need at least one Democrat to support it.

Even some Senate Republicans were skeptical about the chances of McDonnell's plan passing the legislature. Sen. John Watkins, R-Midlothian, commended the governor for putting a proposal on the table but suggested the Senate may devise its own plan.

"I think if we come up with a solution, [McDonnell] will come with us," Watkins told his colleagues.

Watkins, who has proposed imposing a 5 percent tax on wholesale gasoline, warned that any proposal must also be able to make it through the House, where all 100 members are up for re-election this fall. The House and Senate each passed competing transportation packages last year, but then each killed the other's proposal.

Another concern with McDonnell's plan is the fact that it counts on collecting $200 million a year in sales taxes charged to online purchases, but Congress must first approve the imposition of such a tax. One aide to a Democratic Congressman said congressional approval is a long shot because conservative lawmakers view the online levy as a tax increase.

Also looming is this year's gubernatorial election, and so far neither of McDonnell's potential successors are backing his plan. Republican Attorney General Ken Cuccinelli praised McDonnell for presenting "fresh and innovative ideas," but he remains silent on the specifics of the package and his staff did not clarify whether he endorsed it.

Democrat Terry McAuliffe, Cuccinelli's likely opponent, said only that he is "taking a serious look at Gov. McDonnell's proposal."

McDonnell, in his final year as governor, vowed to keep lawmakers in Richmond until they approve a roads plan. Democrats doubted he would.

"I don't know how he's going to keep us here," Howell said. "Handcuff us to our desks?"