Joe Biden’s campaign spent $10 million on television advertising in Pennsylvania last month, as the Democratic nominee maintained his lead in the polls and President Donald Trump halted his TV spending in the state.

The Biden campaign spent an additional $5 million through Labor Day, while Trump remained off the Pennsylvania airwaves during the first week of September, according to the ad tracking firm Advertising Analytics. In all, Biden outspent Trump by $15 million to zero over the course of about five weeks.

The spending advantage is notable given that Trump won Pennsylvania by less than one percentage point in 2016 and faces a relatively narrow path to reelection. It’s also a sign that the Trump campaign has burned through much of the huge cash advantage it built during the Democratic primary contest.

Nationwide, the Trump campaign spent just $4.8 million on TV during the last two weeks of August, a fraction of Biden’s $35.9 million in spending, the New York Times reported.

In Pennsylvania, the Trump campaign has reserved about $370,000 in airtime this week and a total of $5.6 million worth of TV advertising for the month of September, according to Advertising Analytics. That’s about half of the Biden campaign’s $11.8 million in ad reservations. The reservations for future airtime don’t necessarily have to be booked and paid for by the campaigns.

Surveys show Biden with a four-point lead over Trump in Pennsylvania, according to the Real Clear Politics average of the most recent polls, and both parties expect a tight outcome in the state.

The Trump campaign paused its advertising in Pennsylvania and other states at the end of July, when the president announced a shakeup of his campaign leadership. Under campaign manager Bill Stepien, the campaign targeted battleground states that begin voting early, like North Carolina and Florida.

Trump, Vice President Mike Pence, and other campaign surrogates have made multiple trips to Pennsylvania over the past few weeks, ensuring local media coverage. Pence is scheduled to swing through Western Pennsylvania on Wednesday, and both Trump and Biden plan to commemorate the 19th anniversary of the Sept. 11, 2001, terrorist attacks on Friday in Shanksville, where a hijacked plane crashed.

Trump is rarely far from the center of the news cycle, perhaps mitigating the importance of paid advertising. And he was outspent significantly by Hillary Clinton in 2016 and still prevailed. But television ads convey a focused message in a way Trump himself often does not.

Trump did get some air cover last month from GOP outside groups, which spent about $11 million on commercials attacking Biden. Pro-Biden groups spent about $6 million.

Trump campaign spokesperson Courtney Parella accused Biden’s “handlers” of “trying to use an ad blitz to overcompensate for a candidate in hiding and his burdensome policies,” like a tax plan that would raise $4 trillion over 10 years to fund various initiatives on issues like climate change and health care.

“Team Trump is able to be more strategic with our ad placement," she said in a statement. “Unlike Biden, President Trump has been connecting directly with the American people for years and building on his record of success by revitalizing our economy, restoring jobs, producing a coronavirus vaccine in record time, and ultimately delivering the Great American Comeback.”

Brendan McPhillips, Biden’s Pennsylvania state director, said the campaign is “making historic investments to reach voters in every region of Pennsylvania and share Joe Biden’s plans to rebuild our economy in the wake of Trump’s disastrous mishandling of the economy and the COVID-19 pandemic.”

“Joe Biden’s message continues to resonate with Pennsylvania voters because they know he can lead America out of this crisis, get our economy back on track, and create good-paying jobs,” McPhillips said in a statement.

Biden’s campaign ads have highlighted his plans to mitigate the spread of the coronavirus, rebuild the economy, provide affordable health care, and promote racial justice and police reform.

Commercials aired by GOP groups have tried to tie Biden to calls by some left-wing activists to “defund the police," and portrayed the former vice president as hostile to fracking, the controversial drilling technique.