Groups that lobby Virginia’s General Assembly — including some of the state’s largest and most influential businesses — have donated millions of dollars to legislative candidates running in this fall’s campaign.

Dominion Resources, the state’s largest energy provider, has contributed the most — $430,494 — to legislative candidates since the election cycle began, in January 2010, according to the Virginia Public Access Project (VPAP), a nonpartisan group that tracks money in politics. (The donations do not include those from partisan committees.)

The Richmond-based company is followed by the Virginia Bankers Association ($370,822); the Virginia Hospital and Healthcare Association ($277,902); Alpha Natural Resources coal company ($252,907); Verizon ($227,660); the Virginia Trial Lawyers Association ($216,742); the Medical Society of Virginia ($189,746); Altria, the parent company of Philip Morris and one of the world’s largest cigarette manufacturers, ($171,500); the Virginia Cable Telecommunications Association ($151,477); and Appalachian Power ($153,150).

“Contributions are all about the opportunity to be heard,’’ said Jack Harris, executive director at the Virginia Trial Lawyers Association, which represents more than 2,000 lawyers across the state. “I don’t see that there is anything wrong with it.”

Katharine Webb, senior vice president of the Virginia Hospital and Healthcare Association, said her organization’s political action committee raised $25,000 in its first year, about two decades ago. That amount has increased tenfold in this cycle as it helps candidates pay for TV and radio advertising and direct mail.

“Health care has a lot of moving parts. That’s tough for a part-time legislator,’’ Webb said. “The people that ask questions and are interested, we’re helping them. Listening comes first and then comes money. Giving is all about relationships.”

Both the lawyers group and the hospital and health-care association successfully lobbied legislators this spring to override Gov. Robert F. McDonnell’s veto of a bill that will raise awards in medical malpractice lawsuits by $50,000 a year starting in 2012.

In total, Republicans had a nearly 2-to-1 advantage over Democrats as of the last reporting period, which ended June 30, according to an analysis by VPAP, as the GOP looks to take control of the state Senate and add to the party’s majority in the House of Delegates.

Republicans had $13.7 million in the bank, compared with $7.4 million for Democrats, including committees controlled by candidates, parties and legislative leaders.

Virginia is one of a handful of states that don’t limit donations, a system that some argue has led to costly campaigns and candidates who cater to Richmond interests and wealthy donors.

State law bans legislators and statewide officeholders from raising money during the General Assembly’s annual session, which will begin in January, but they make up for it in the days before they convene with a flurry of activity. They are required to disclose all contributions.

After the General Assembly passed a bill clarifying that martial arts schools should not be licensed as child day-care centers, Del. Timothy D. Hugo (R-Fairfax), the bill’s sponsor, received 14 donations from martial arts instructors totaling $9,750. Hugo reported the contributions in the three-month period that ended June 30.

The measure garnered little attention during the legislative session that ended in February. It passed the Republican-controlled House of Delegates and the Democratic-led Senate unanimously and was signed into law by McDonnell (R).

Hugo did not return a call seeking comment. But in a statement posted on the Republican Party of Virginia’s Web site during the session, he said he introduced the measure on behalf of a martial arts academy in Centreville. He also said treating martial arts schools the same as day-care centers would be “detrimental” to most, if not all, schools.

Most donors interviewed said they do not consider political party when deciding which lawmakers get contributions. Instead, contributors said they consider legislators’ key votes, stances on issues, leadership positions and committee memberships.

“We go to a great extent to be party neutral,’’ said Geoffrey T. Harter, chairman of the Medical Society of Virginia PAC. “Our members are not always thrilled about that.”

Lobbying firms and individual lobbyists gave almost exclusively to incumbents, according to a VPAP analysis of donations between Jan. 1, 2010, and June 30.

Lobbyists gave $7.4 million — or 99.6 percent of donations — to incumbents; $25,600 — or 0.34 percent — to candidates vying for open seats;and $3,200 — or 0.04 percent — to challengers.

Thirty-one incumbents received 75 percent or more of their donations from lobbyists or lobbying firms, according to VPAP.

Del. Scott A. Surovell (D-Mount Vernon) received the least amount of money in percentage — 9 percent — from lobbyists of all legislators running for reelection, according to VPAP.

Surovell, elected in 2009 and a former chairman of the Fairfax County Democratic Committee, said that as a freshman in the minority party, he doesn’t receive many contributions from large lobbying firms.

“I’m a freshman Democrat in a caucus that has 39. Richmond special interests don’t have a lot of interest in anything I have to say,’’ he said.

But, he said, he has managed to raise a considerable amount — $150,705 in the cycle — from those he has met through his law practice, community and activities in Northern Virginia. “I don’t have to rely on Richmond to fund my campaign,’’ he said.

In Southside Virginia, one of the most high-profile House races is already clashing on campaign contributions.

Minority Leader Ward L. Armstrong (D-Henry), who moved after redistricting placed him outside of his House seat, recently accused his opponent, Del. Charles Poindexter (R-Franklin), of collecting $100,000 from electric companies through Republican leaders.

But Armstrong did not disclose that he had taken the same amount from electric companies and those associated with them since 2007 — the year Poindexter was elected.

Armstrong said in an interview that the difference is that he’s fighting the companies on their skyrocketing rates and his opponent is not. “He’s done nothing,’’ he said.

Republicans have their considerable funding advantage largely because they hold many key positions in state government, including all three statewide offices — McDonnell, Lt. Gov. Bill Bolling and Attorney General Ken Cuccinelli II — as well as top posts in the House.

McDonnell has more than twice as much money as did his Democratic predecessor, Timothy M. Kaine, at a similar point. McDonnell had $2.9 million as of June 30, while Kaine had $1.3 million on the same date in 2007, the year Democrats took control of the Senate.

Consol Energy, one of the nation’s largest coal mining companies, has donated the most money — $157,010 — to McDonnell’s PAC, Opportunity Virginia, since the start of the election cycle, in January 2010, according to VPAP.

The Pittsburgh company is followed by Bob Perry, a Houston homebuilder and major political contributor ($125,000); Perry’s wife, Doylene Perry ($125,000); Richard Gilliam, founder of Cumberland Resources coal mining company ($100,000); Randal J. Kirk, a billionaire Radford businessman ($100,00); Star Scientific tobacco company ($79,868); Alpha Natural Resources (75,000); Marvin Gilliam, a Cumberland executive ($75,000); Smithfield Foods ($60,000); and Wal-Mart ($51,000).