Bill and Hillary Rodham Clinton watch over Virginia Gov. Terry McAuliffe (D) at his inauguration in January 2014. More than $1 for every $5 the governor has raised has come from a single donor. (Ricky Carioti/The Washington Post)

The Democratic Party of Virginia has a Million Dollar Man — a billionaire’s son and resident of New York with no obvious connection to the commonwealth.

Philip Munger has written four six-figure checks since June, adding up to $1 million for a party that has pulled in less than $1.6 million in direct donations this year. That has made him the largest individual donor to the state party in the past 20 years, if not all time.

Even factoring in the $3.2 million that Gov. Terry McAuliffe (D) raised through his political action committee, Munger’s money accounts for more than $1 for every $5 that the governor has raised through the party and his PAC ahead of critical state elections, which on Tuesday will determine control of the state Senate.

Munger is the son of Charles Munger Sr., Warren Buffett’s partner in Berkshire Hathaway. Across the country and the political spectrum, one of his brothers has been propping up the Republican Party in his home state of California for the past decade.

McAuliffe has the power to tap that sort of deep-pocket donor as a longtime friend of and fundraiser for Bill and Hillary Rodham Clinton. And the money he brings in this year is key — to Democrats’ chances for winning the Senate, to McAuliffe’s own prospects for a legislative legacy and to the party’s odds of taking the White House in 2016. Democrats in this key swing state have been spending heavily in data and field operations for use this year and next, when Hillary Clinton hopes to be the Democratic nominee for president.

McAuliffe’s ability to hit up a single super-rich source for a string of contributions represents political moneymaking at its most efficient, supporters say, allowing McAuliffe to spend more time on the business of governing a state that is home to more than 8 million residents.

But that fundraising strategy also makes the party highly dependent on the whims of a single individual, one who could easily drift away once the term-limited governor moves on in 2018. It also runs contrary to the populist zeitgeist of the party base these days, as Democratic socialist Bernie Sanders gives Clinton a run for her money in the Democratic presidential primary.

Reached on his cellphone a week ago, Munger said he was in Germany and too busy at that moment to discuss his donations to the party. He did not respond to subsequent messages seeking comment.

Munger has delivered four checks this year to the party — one for $100,000, two for $250,000 and one for $400,000. Officials with the state party and the governor’s PAC declined to discuss Munger’s largesse in detail, sticking to broad appreciation.

“The Governor and the party appreciate the contributions of Philip Munger and all of our donors who have played a major part in expanding the party’s capabilities,” Brian Zuzenak, political director for McAuliffe’s Common Good VA PAC, said via e-mail. “Thanks to our supporters, the party will continue to follow the Governor’s progressive approach to getting results for the Commonwealth.”

Party press secretary Morgan Finkelstein would say only this: “We’re grateful for his support.”

The Republican Party of Virginia, like its Democratic counterpart, has struggled financially in recent years, but Chairman John Whitbeck said the GOP is better off with smaller-dollar donors who live and vote here.

“We’re proud of the fact that our donors have given everything from $1 to $50,000, good people and hard-working Virginians that invest in our party,” Whitbeck said. “He [Munger] doesn’t have a vote. If he’s trying influence Virginia elections, Tuesday will tell us what he’s getting for his million dollars.”

Munger and the outsize role he has played in party finances are little known in Virginia Democratic circles, even among senior elected officials.

“I don’t know him,” said Senate Minority Leader Richard L. Saslaw (D-Fairfax). “To be honest, I had heard the name. I had no idea it [Munger’s financial contribution] was to that extent.”

But Saslaw, who made his living with service stations, said it was a bonus to have a governor with far-flung connections. He marveled at meeting Lady Lynn Forester de Rothschild in Alexandria a week ago, during a rally with Hillary Clinton and McAuliffe. The Clinton mega-donor is married to a knight descended from what Forbes calls “one of the world’s oldest private banking families.” De Rothschild was in the crowd as Clinton touted her many small-dollar contributors, then spent the weekend as McAuliffe’s guest at the governor’s mansion.

“He knows people the average elected official wouldn’t know,” Saslaw said. “The guy’s got a Rolodex to die for, from what I’m told. The reason he only raised $40 million” — a record amount for a Virginia governor’s bid — “was he only got through the Ds in his Rolodex.”

McAuliffe tapped many rich out-of-state donors during his 2013 race to amass that enormous war chest. After his win, Democrats and Republicans alike expected that legendary fundraising prowess would fill PAC and party coffers to overflowing. It hasn’t. So far, McAuliffe has raised the same amount for his PAC — $5.7 million — as his predecessor, former governor Robert F. McDonnell (R), had at the same point in his term.

The party and PAC reported raising a combined $8.5 million this year through September, but when transfers and other activities that do not contribute to the bottom line are factored in, the total is $4.8 million, Zuzenak said.

Munger has been a substantial donor to Hillary Clinton and President Obama. He also is a policy analyst, investor, educator, philanthropist and consultant, according to information he supplied when donating to other Democrats this year. In some instances, he listed his employer as the New School, a progressive university in New York. His name does not appear in the current online faculty directory. A call to the school’s human resources department was not immediately returned.

Munger is part of a large bipartisan brood of children and stepchildren raised in California by Charles Munger Sr. Two of his siblings have been high-profile political donors in that state. Charles Munger Jr., is a Stanford physicist and moderate Republican. Molly Munger is a civil rights lawyer and liberal-leaning independent.

Charles Jr. and Molly Munger did not respond to messages seeking comment. But in a 2012 interview with the San Jose Mercury News, Charles Jr. described their political activities as a civic duty.

“We both could amuse ourselves with art collections, golf and writing the great American novel,” he told the newspaper. “But we chose our parents wisely. They were always involved in civic service and gave us the sense we owed a great deal to society.”

Molly Munger has faded from the political scene since 2012, according to Republican strategist Kevin Spillane. But Charles Jr., who made his first political contribution to Arnold Schwarzenegger more than a decade ago, is active.

“If it weren’t for Charles Munger, the California Republican Party would have been driven into the sea at this point,” Spillane told the Los Angeles Times earlier this year, when it calculated that he had poured $78 million into the party and various campaigns.

There has been some pushback, both from conservatives who dislike the professorial physicist’s moderate bent and from fellow moderates worried about relying so heavily on a single donor. He has been mocked on a blog called “The Munger Games,” which bills itself as the watchdog of the “one-man maelstrom of money intent on re-making California Republicanism in his bow-tied image.”

Similarly, several Democratic Party members in Virginia expressed concern when The Washington Post informed them about the size of Philip Munger’s contributions. Some praised McAuliffe for snagging the hefty contributions, but also expressed hope that the money gets plowed into a diversified fundraising program to sustain the party.

“If I were them, I would try to put some of this away as seed money and hire fundraisers. They need to have a grass-roots program,” said one Democratic activist, who spoke on the condition of anonymity in order to frankly discuss party finances. “What would concern me more is — is the money coming in because it’s Terry McAuliffe? Because it’s only going to be Terry McAuliffe for two more years.”