Even as a Senate committee cleared Gov. Bob McDonnell's transportation plan Thursday, it raised serious doubts about whether the package will survive without significant changes.

Several Senate Finance Committee Republicans voted to send the package to the full Senate, but they also expressed reservations about getting rid of the gas tax and raising the sales, the cornerstone of McDonnell's plan to fund roads. All five Democrats on the committee opposed the package.

The House Finance Committee approved McDonnell's plan Wednesday night. Both the Senate and the House will likely vote on the measure next week, but most of the work on the proposal will come in the following weeks, when lawmakers meet behind closed doors to hammer out a compromise that can pass both chambers.

The governor's office estimates the plan will raise $3.1 billion over the next five years. In addition to eliminating the gas tax -- which would make Virginia the first state to do so -- and raising the sales tax to 5.8 percent, McDonnell wants to raise registration fees and slap an annual fee on alternative fuel vehicles. He would also tax online purchases, though that needs approval from Congress, and shift 0.25 percent of the sales tax from the general fun to roads.

McDonnell needs at least one Democratic vote to get his package through the evenly divided Senate.

"Our investment in building and maintaining our highways, transit systems and railroads is of utmost importance to the citizens of Virginia and they have told us loud and clear that now is the time to get something done on this issue," McDonnell said. "Today's action is another major step forward in our effort to enact a long overdue, long-term transportation funding solution."