An environmentalist billionaire is putting another half-million dollars into the effort to beat Attorney General Ken Cuccinelli II, the latest sign that outside groups plan to pour cash into the Virginia governor’s contest.

Tom Steyer -- a San Francisco-based financier who previously put $400,000 behind an ad attacking Cuccinelli for his legal efforts against then-University of Virginia climate researcher Michael Mann — is upping the stakes. NextGen Climate Action Committee, a super PAC bankrolled by Steyer, is putting roughly $500,000 into a new ad that makes a broad attack on the ethics of Cuccinelli, who is squaring off against businessman Terry McAuliffe (D).

The ad, titled “Now,” will run for roughly 10 days in the Richmond, Norfolk and Roanoke markets, according to a memo issued by the PAC, which called it “the first in a series of ads we plan to do” about Cuccinelli.

“Lavish meals. Travel on private jets. Just some of the gifts Ken Cuccinelli took in the Star Scientific scandal,” says the ad’s narrator. “Now Cuccinelli’s office is under investigation for secretly helping an out-of-state energy company that was drilling natural gas from Virginians’ private property but refusing to pay royalties. The same company that gave Cuccinelli $100,000 in campaign contributions. Gifts, trips, investigations. Ken Cuccinelli: Helping himself, not us.”

The ad seeks to tie together the two main issues Democrats have been using to attack Cuccinelli’s integrity. Cuccinelli accepted $18,000 worth of gifts from Star Scientific chief executive Jonnie R. Williams Sr., whose gifts to Gov. Robert McDonnell (R) and his family are the subject of a federal investigation. Cuccinelli, who initially failed to disclose some of the gifts, has said he did nothing to help Williams or Star.

Separately, the state Inspector General is investigating allegations that an assistant in Cuccinelli’s office gave improper legal help to two energy companies battling Southwest Virginia landowners in court over royalties from gas drilled on their land. One of the companies, Consol Energy, has given more than $111,000 to Cuccinelli’s gubernatorial campaign. Cuccinelli himself is not under investigation, and his office has defended the work of the assistant involved in the case.

The Virginia Republican Party fired back at the ad Wednesday evening.

“Virginia voters aren’t easily fooled,” said state GOP spokesman Garren Shipley. “They know that the man who behind these false attacks: an environmental extremist California billionaire aiding Terry McAuliffe. They also know that millions of dollars in ads come with a price: the expectation that Terry McAuliffe - who said ‘I never want another coal plant built’ - will carry out a destructive energy policy that will bankrupt the coal industry and make energy prices skyrocket for all Virginians.”