Northern Virginia, the state’s economic engine and population center whose growing outer suburbs drove the latest round of legislative redistricting, boasts more primary elections than any other part of Virginia this year.

Of the 19 General Assembly primaries in Virginia in August, half are in Northern Virginia, including six for the state Senate and three for the House of Delegates.

The diverse crowd of 21 candidates, recently certified by the State Board of Elections, is made up of many familiar faces, some who previously held office or were active in politics.

The field for the Aug. 23 primaries includes a former delegate perhaps best known for distributing plastic models of fetuses to lawmakers preparing for an abortion vote; the state’s only openly gay legislator; a local businessman made famous at a Sarah Palin rally; and one of the first Hispanic women to run for the House.

Republicans are in a fierce battle to take control of the Senate, where Democrats hold a fragile 22 to 18 majority. If successful, it would be the second time since Reconstruction that the party held the governor’s mansion, House and Senate at the same time in Virginia.

Gov. Robert F. McDonnell and Speaker William J. Howell (Stafford) are looking for allies to pass school choice bills, immigration enforcement, pension reforms and other priorities that have died in past years at the hands of a Democratic-led Senate.

Already, Republicans have far outpaced Democrats in recruiting. Republicans have candidates running in 108 of the state’s 140 General Assembly districts — compared with just 75 for the Democrats, according to the Virginia Public Access Project, a nonpartisan tracker of money in politics.

In the Senate, Democrats have candidates in the 24 districts where they hold the seat or where it is up for grabs, including the two newly added districts. They have not yet fielded candidates in any of the seats where a GOP incumbent is running. Republican have candidates in 36 districts, 25 of them already certified as nominees.

“I think all the energy right now, politically speaking, is on the Republican side,’’ said Lt. Gov. Bill Bolling (R), who presides over the Senate. “I think that’s true on the national level, and I think it’s true at the state level. We probably have more Republican candidates running in the Senate than we ever have had before.”

Republicans are eyeing possible pickups in Southside, Hampton Roads and the southwest area. They also are hopeful that they can take both new Senate seats — one located in Northern Virginia and the other west of Richmond — and possibly the seat held by Democratic Sen. Linda “Toddy” Puller, which includes portions of Fairfax, Prince William and Stafford counties.

Senate Majority Leader Richard L. Saslaw (D-Fairfax) said his party is still recruiting candidates and expects to be competitive in the new districts and in the Republican-leaning district of a retiring longtime Republican senator in southwest Virginia. “It ain’t the quantity of candidates you have, it’s the quality,’’ Saslaw said.

Aug. 23 is also the deadline for filing to run in the general election in November.

Saslaw said Senate Democrats have about $1 million in the bank to give to candidates and expects to raise an additional $1.5 million before the November elections.

Figures from the fundraising period, which ended Thursday, were not yet available. Officials with the Senate Republican caucus and McDonnell’s political action committee, Opportunity Virginia, declined to release updated numbers.

The most recent numbers available show Opportunity Virginia with $1.9 million cash on hand and the Senate Republican caucus with $853,000 in the bank as of March 31, according to VPAP. The Democratic caucus had $1 million and Saslaw had $860,000.

Since then, both caucuses have held huge fundraisers. The Democrats recently raised $500,000 for the House and Senate at the posh Homestead mountain resort last week. Senate Republicans took in $350,000 at their retreat in Williamsburg last month.

The General Assembly drew new maps this summer to bring the 140 districts of the Democratic-controlled Senate and Republican-held House of Delegates into alignment with population shifts detailed in the 2010 Census. The plans give Northern Virginia a new senator and three new delegates, all in the region’s growing outer suburbs.

In the new 13th Senate District, which takes in parts of Loudoun and Prince William counties, Republicans will have a three-way primary in August. Prince William Supervisor John T. Stirrup faces former Loudoun Del. Dick Black, perhaps best known for distributing plastic models of fetuses to lawmakers as they prepared to vote on an abortion bill, and Prince William chief deputy clerk and small-business owner Bob FitzSimmonds, who has unsuccessfully run for the Senate before.

For the 36th Senate District seat held by Puller, Jeffrey M. Frederick, ousted leader of the Republican Party of Virginia and a former Prince William delegate, faces Tito Munoz — better known as “Tito the Builder” — the owner of a small construction business who made a name for himself when he appeared onstage with Palin during the 2008 presidential campaign.

In the 37th Senate District, which is represented by David W. Marsden (D) and includes Fairfax, two Republicans are running in the primary — Jason Flanary, executive director of CapNet, which lobbies on technology issues, and Steve Hunt, a retired naval flight officer and former Fairfax school board member who ran for the seat before.

In the 39th Senate District held by Sen. George Barker (D), which includes Fairfax and Prince William as well as Alexandria, Miller Baker, a constitutional lawyer at a Washington firm, and Scott Martin, an assistant dean and associate professor at George Mason University, are running in the GOP primary.

Two reliably Democratic seats are open because of the retirements of Sen. Mary Margaret Whipple (D-Arlington) and Sen. Patricia S. Ticer (D-Alexandria).

In the 31st District, which is held by Whipple and includes parts of Arlington, Fairfax and Loudoun counties, Arlington County Board member Barbara Favola faces Jaime Areizaga-Soto, who formerly worked for the general counsel’s office at the U.S. Agency for International Development.

In the 30th District, which is held by Ticer and includes parts of Arlington and Fairfax as well as Alexandria, Del. Adam Ebbin (D-Alexandria), the legislature’s only openly gay member, faces Arlington School Board member Libby Garvey and Alexandria City Council member Rob Krupicka.

In the House, Howell said Republicans expect to pick up three or four seats to add to their already hefty 61-member caucus after a strong legislative session. The chamber’s Democratic leader, Del. Ward L. Armstrong (Henry), said Howell “certainly did the best he could to gerrymander’’ the map during redistricting. But Armstrong still thinks his party can be competitive in some seats, particularly new ones in the outer suburbs of Northern Virginia, which swing back and forth between the two parties.

The three new House seats in Northern Virginia include two largely centered in the growing counties of Loudoun and Prince William and one that includes another portion of Prince William and a part of Stafford.

In the primary for the new 87th District, which includes Loudoun and Prince William, Jo-Ann Chase, a real estate broker who serves on the Republican Party’s State Central Committee and is one of the first Hispanic women to run for the House, faces David Ramadan, an international consultant who is on the George Mason University Board of Visitors.

In the new 10th District, which includes Clarke, Frederick and parts of Loudoun, Republicans have a three-way primary. Lawyers Randy Minchew and John Whitbeck face Cara Townsend, a small-business owner.

Ebbin’s decision to run for the Senate has left his solidly Democratic 49th District, in Arlington and Fairfax, up for grabs.

Alfonso Lopez, who worked for the U.S. Small Business Administration and was Gov. Timothy M. Kaine’s director of the Virginia Liaison Office, faces Stephanie Clifford, director of special events at the Podesta Group.