Add one more data point to the theory that Virginia is losing its status as a swing state: Outside interest groups and super PACs spent zero dollars on presidential TV advertising in the state last month.

Four years ago, when Mitt Romney challenged President Obama, such groups spent almost $10 million.

The figures were compiled by the Virginia Public Access Project from filings at major network affiliates in the state’s four biggest television markets — Washington, Hampton Roads, Richmond and Roanoke.

Polls have suggested that Democrat Hillary Clinton has a sizable lead over Republican Donald Trump in Virginia — last month’s Washington Post poll had her up 8 percentage points. Demographic shifts, especially in the D.C. suburbs, seem to be painting a layer of blue over a state that had been reliably red.

[See how Virginia voters feel about the race in a new 50-state poll]

That may lead outside groups to hold onto their money for more competitive states, said Steven Farnsworth, a political scientist at the University of Mary Washington.

That’s the calculation being made by Democratic super PAC Priorities USA Action, which is focusing elsewhere because “it’s clear that Virginia is simply more challenging for Donald Trump than some of the closer states that we’re still fully engaged in,” said spokesman Justin Barasky.

Clinton’s selection of former Virginia governor Tim Kaine as her running mate “is probably going to add a couple of points to the Democrats’ margin in Virginia, and that makes it a bit tougher sell for ad buys that would be targeting the most swingy of the swing states,” Farnsworth said.

But don’t touch that dial just yet. Farnsworth sees an opportunity for Trump, who covets Virginia’s 13 electoral votes in his bid to get the 270 necessary to win.

“It’s clear the Trump campaign is making Virginia one of their priorities, and the electoral map suggests they should. It’s pretty hard for a Republican to win the electoral college without Virginia,” he said.

Crossroads GPS, one of the biggest Republican super PACs, spent nearly $3.6 million in Virginia in August 2012. This year, the group and its affiliates have yet to air presidential ads in any state, concentrating instead on protecting the GOP majority in the Senate. It doesn’t help that Trump has alienated many Senate Republicans, who have close ties to Crossroads and its related Senate Leadership Fund.

But Crossroads spokesman Ian Prior said the group could yet broaden its focus. “Whether Crossroads gets involved in some way in the presidential [race] remains to be seen,” he said. “We’re keeping our options open.”

Viewers who may have enjoyed a lighter-than-usual menu of pre-Labor Day political ads, take note: Tightening poll numbers, Farnsworth said, “suggest maybe there should be more.”