— The two chambers of the divided Virginia General Assembly approved new state legislative boundaries drawn up by political leaders in each body, probably establishing partisan districts that will be used for the next decade.

For Northern Virginia, the plans will mean a new senator and three new delegates, all in the region’s growing outer suburbs, as the legislature redraws lines to accommodate population shifts revealed by the once-a-decade census.

It is a highly political process used by both parties to improve their electoral strength and protect incumbents.

The GOP-led House of Delegates approved a plan to redraw House districts late Wednesday. On Thursday, the Democratic-led Senate agreed to add plans for Senate districts to the measure. After a final vote likely to take place Monday, the legislative plan will head to Gov. Robert F. McDonnell (R) for his signature.

Also Monday, the General Assembly is to start debating about how to redraw the state’s 11 congressional districts. The House publicized one proposal Thursday.

House Republicans managed to snag a largely bipartisan 86 to 8 vote in support of their proposal. The margin might have been influenced in part by a perception that the GOP’s solid hold on the 100-member body, which includes 60 Republicans, is unlikely to budge in the next decade.

A handful of Democrats voted against the bill, including House Minority Leader Ward L. Armstrong (Henry) and others whose districts were collapsed in the plan.

In about two hours of debate, some Democrats asked Del. S. Chris Jones (Suffolk), the Republican architect, about the plan as they prepared for an almost inevitable lawsuit contending that Republicans could have drawn two additional majority-minority districts but chose not to.

“This bill is flawed,” Armstrong said.

Despite that, every member of the Legislative Black Caucus voted for the plan — and many spoke in favor of it, saying that their views had been taken into account as the plan was drawn.

The Democrats’ plan in the state Senate, on the other hand, was adopted in a straight party-line vote of 22 to 18. Control of the Senate, narrowly won by Democrats in 2007, will be hotly contested in November.

Republicans in the Senate said the Democratic plan divides up too many counties and cities and contains districts that vary too widely in population.

They seemed especially chagrined about districts in Virginia Beach, where Democrats agreed to merge the districts of two incumbent Republicans to accommodate falling population in the Hampton Roads region.

“The partisan affiliation is the sole community of interest that exists with this plan,” said Sen. John C. Watkins (R-Chesterfield).

Democrats said that their plan complies with federal and state laws and that it was guided by principles similar to those behind the Senate map drawn up 10 years ago by Republicans.

There had once been fear that the legislature could stalemate over redistricting plans because this is the first time since Reconstruction that the process has been undertaken by a divided legislature.

But the General Assembly has avoided deadlock through an informal agreement between the two chambers: Republicans in the House agreed to accept Senate lines drawn by Democrats, and Democrats in the Senate agreed to accept House lines drawn by Republicans.

Work on congressional maps next week could go less smoothly. The Legislative Black Caucus has called for the General Assembly to redraw the maps so that black voters are a majority in one district and a sizable minority in a second. Now, the state has just one majority black congressional district.

Democrats in the Senate had not filed a congressional proposal, but Sen. Janet D. Howell (D-Fairfax), who chairs the redistricting committee, said Thursday that she doubted the Senate proposal would mirror the House’s, raising the possibility of a legislative deadlock.

“I think this is the beginning of the process, not the end,” said U.S. Rep. Gerald E. Connolly (D-Va.). “We’ll just have to see.”

Although the political detente over state legislative lines has allowed the General Assembly to avoid a messy fight that could have derailed the timing of November’s state elections, it has incensed government watchdog groups that have long said that redistricting should be performed by disinterested bipartisan voices instead of politicians.

“The legislature, particularly the House of Delegates, has done exactly what the redistricting watchers have feared — pushing through plans that protect incumbents,” said C. Douglas Smith, director of the Virginia Interfaith Center for Public Policy and chairman of the Virginia Redistricting Coalition, which advocates for changing the process.

They will soon lobby the governor to use his power to amend legislation approved by the General Assembly, scrapping the political plans and replacing them with ones drawn up by a bipartisan advisory commission McDonnell had appointed.

McDonnell said Thursday that he intends to examine the plans closely after they are approved.

“What I have told everybody is, I will look at it when I get it,” he said. “I will make sure first and foremost it is legal — that it complies with state and federal law.”

Staff writer Ben Pershing contributed to this report.