Update, 5:13 p.m.: Several Republican senators emerged from their closed-door meetings and said more negotiations are needed on the plan. “There is no deal,” said Sen. Ryan T. McDougle (R-Hanover). “We're here tonight. We're talking.”

Sen. John C. Watkins (R-Chesterfield) said Republican negotiators had presented a plan to their colleagues. But, he noted, “there's no deal until the Senate Republican and Democratic caucus agree to it.”

Original post: Senate Democrats and Republicans reached a tentative deal Wednesday afternoon on new state legislative boundaries, Sens. Mary Margaret Whipple and Jill Holtzman Vogel (R-Winchester) said.

The 40-member Democratic-led Senate will vote on the plan Thursday, and both senators said they expected the proposal to receive bipartisan support — which the initial plan vetoed by Gov. Bob McDonnell lacked.

Whipple (D-Arlington) said the breakthrough came as Republicans agreed that the Hampton Roads area would lose a senator because of population loss and Democrats agreed a new district that had been draw in the Richmond region would shift to the west. That district would be more politically competitively than it would have been under the original plan proposed by Democrats.

But Whipple said she believed the new map would still allow Democrats to keep their majority. “I think it preserves 22 to 18,’’ she said.

She said that while she doesn’t know whether McDonnell will sign off on the bill, she believes the governor is probably willing to sign anything with bipartisan support.

“If the Senate Republicans go to him and say, ‘We’re agreed,’ I think he’ll agree,’’ Whipple said.

McDonnell vetoed the first redistricting bill, saying legislators had sent him maps that might violate state and federal laws and that split too many counties, cities and towns. He also faulted the Senate for sending him a bill that had no Republican support.

Both the Republican and Democratic caucuses are being briefed on the proposal.

Sen. John C. Watkins (R-Chesterfield) confirmed the contours of the map now under discussion but said he doesn’t anticipate a 40 to 0 vote in support. “It’s not that good of a deal,” he said.