Senate Republicans surprised everyone Monday by ramming through a vote for new district maps that improve their political fortunes, winning majority of support for it because a Democratic lawmaker was attending the inauguration.

The power play occurred when Sen. John Watkins, R-Midlothian, introduced a bill amendment that significantly redraws Senate district boundaries so Republicans can potentially pick up an additional seat in the 2015 elections. The new map means two senators -- Democrat Creigh Deeds and Republican Emmett Hanger -- will have their districts combined.

Republicans said it was an effort to correct maps passed in 2011 that split communities. The new maps also create a sixth majority-minority district.

Any changes must be approved by the Justice Department because of Virginia's history of voter suppression.

"These new districts are drawn in full compliance with Virginia's traditional redistricting criteria," Watkins said. "Therefore, it appears that if litigation were brought under the Voting Rights Act, this plan would have a very high likelihood of success."

The changes were approved 20-19 along party lines. One Democrat, Sen. Henry Marsh, was in D.C. for President Obama's inauguration, providing an opportunity for Republicans to make their move. The bill had been passed by for nearly two weeks as Republicans waited for a Democrat to miss a day. Lt. Gov. Bill Bolling, a Republican, was against the plan and likely would have used tie-breaking powers to vote against it if it came to him.

The bill now goes to the House for approval.

"[Bolling] fears that this action could set a dangerous precedent for future redistricting actions, and he is concerned that it could create a hyper-partisan atmosphere that could make it very difficult for us to address other important priorities," Bolling spokeswoman Ibbie Hedrick said.

Democrats were outraged and vowed to take legal action to fight the change. They also warned that the surprise maneuver threatens the already fragile relationship between the two parties.

"The collateral damage from this thing will be immeasurable," Senate Minority Leader Dick Saslaw said. "This isn't the last we've heard of this."

A breakdown in the Senate could have severe implications for Gov. Bob McDonnell, who is trying to push through massive transportation and education reforms to cement his legacy before his term expires in a year. Any plan to fund road work will need Democratic support to pass the Senate.

McDonnell spokesman Tucker Martin said the Republican governor was "very surprised" by the vote.

"The governor's priorities this session are transportation, education and the budget," Martin said. "Not redistricting."