Northern Virginia voters largely stuck with Democratic incumbents Tuesday as Republicans waged a fierce battle to cement power in Richmond by taking control of the state Senate.

With four-fifths of the vote counted, Sen. George L. Barker (D) led challenger Miller Baker (R) in a district stretching from Prince William County to Alexandria — a map Barker played a key role in drawing. In Fairfax County, Sen. David W. Marsden (D) had a clear lead over Republican Jason Flanary.

Dick Black (R), longtime antiabortion activist and former House delegate, appeared headed for an easy win over businessman Shawn Mitchell (D) in a new Senate district in Loudoun and Prince William counties. Three-term Sen. Linda T. “Toddy” Puller (D) held back an energetic challenge by Jeff Frederick, the former state Republican Party chairman and delegate from Prince William, in a district that snakes from the tip of Stafford County up the Potomac and into Fairfax.

In the race to succeed Sen. Mary Margaret Whipple (D), who is retiring, Arlington County Board member Barbara Favola (D) easily defeated businesswoman Caren Merrick (R) for a seat stretching from Arlington to eastern Loudoun.

The rest of the region’s incumbent senators appeared headed toward victory, as did the area’s sitting House members, even as Republicans gained as many as seven House seats statewide.

Del. Barbara J. Comstock (R) was headed toward a win over businesswoman Pamela Danner (D) in the district including Great Falls and part of McLean. With three-quarters of the vote in, David Ramadan (R) was narrowly edging Mike Kondratick (D) in a district covering portions of Loudoun and Prince William.

The Senate was the main battlefield as Republicans were only about 100 votes in a single central Virginia district from seizing the chamber. Democrats currently hold a 22-to-18 edge in the Senate — their lone power center in a state where the GOP controls the House of Delegates and the governor’s mansion.

Unfettered Republican dominance of the government could have far-reaching consequences for Northern Virginia, where explosive growth has created a thirst for more transportation and education funding and deep resentment against a state government that the region’s politicians say sends a disproportionate number of dollars to less densely populated areas.

The off-year elections — Virginia is one of only four states that hold elections in the year before a presidential vote — routinely draw sparse turnouts. This year, poll watchers reported some confusion as many voters found themselves in newly drawn districts, the result of redistricting that takes place after the census every 10 years.

With the new districts and some long-standing officials retiring or facing stiff challenges, voters in some areas had stark choices. But for 10 of Northern Virginia’s 32 seats, there was no contest at all. Similarly, statewide, 73 of 100 seats in the House of Delegates went unchallenged by one of the two major parties, and 15 of the Senate’s 40 seats offered no choice between a Republican and a Democrat.

Democrats tried to convince voters that complete Republican control would hurt Northern Virginia, leading to cuts in state funding and shifts to the right on gun control, abortion and other social issues.

But Tom Davis, a moderate Republican who represented Fairfax in the U.S. House for 14 years, said GOP control would mean “one-party accountability, instead of the constant finger-pointing you have now.”

Local politicians were watching to see not only if the GOP would win statewide, but also whether Northern Virginia would be in symphony with the rest of the state or find itself going against the grain.

“If we get the Senate majority by winning some seats up here, then it’s good because we have a seat at the table,” said Del. David B. Albo (R-Fairfax). “If we get a majority without winning the seats up here, then it’s going to hurt because the senior Democrats who are from Northern Virginia will no longer be in power.”

Polling places in Northern Virginia weren’t exactly crowded Tuesday, but many people who voted came out to deliver a message for next year’s presidential election — a strong dissent to President Obama’s management of the economy or a statement blaming Republicans for the paralysis in Washington.

“Unfortunately, I have to wait for next year to vote in the one I care most about,” said Tom Mills, retired after 23 years of service in the Army, as he walked into Hayfield Elementary School in the Alexandria section of Fairfax. Mills said he voted to let Obama know that “I think he’s a bum, and that’s being kind. Everything he does is against America.” Mills voted for all the Republicans he could find on the ballot. “That’s step one.”

Three miles away, in Franconia, it was national politics that drew Gary and Mary Buffington to vote at Francis Scott Key Middle School. “I’m a liberal Democrat, and the conservative trend scares me,” said Gary Buffington, 61, a retired Census Bureau statistician.

He and his wife said they voted for Barker, hoping to keep him in office and thwart a GOP takeover of the state Senate. The couple, strong supporters of Obama, also wanted to deliver a protest message against what Gary called “the obstructionist attitude of the Republican Party. Nothing’s getting passed” in Washington.

Democrats sought to pin the “too conservative” label on several Republicans, particularly Black and Frederick.

As Black’s supporters passed through a blizzard of signs for Mitchell outside Emerick Elementary School in Purcellville, voter Susie Twetten recalled that when Loudoun Supervisor James Burton (I-Blue Ridge) knocked on her door, he told her that Black supports banning inappropriate books from public schools. She was impressed.

“We need to be more careful about the books we have in schools,” she said. “Children are very impressionable.”

Staff writers Susan Svrluga and Laura Vozzella contributed to this report.