With less than a month to go until the election, Democrats continue to invest more in presidential advertising than Republicans.

Since Joe Biden dropped out of the race in late July, the Harris campaign and outside Democratic groups have spent $820.4 million on paid media, according to a new report from advertising intelligence and analytics firm AdImpact.

The Trump campaign and outside Republican groups, meanwhile, have spent a total of $510.4 million.

In addition to ads already aired, Democrats also hold an advantage on future ad inventory. At present, the party has booked $266.5 million in advertising until November 5. That’s nearly 50% more than their rivals.

Prior to the Democratic National Convention in August, the Harris campaign announced plans to spend at least $370 million on advertising, with $170 million dedicated to television and $200 million going to digital channels.

“By reserving early, the Harris-Walz campaign is securing inventory during high-viewership moments like major sporting events and other national programs before they sell out,” the Democratic campaign said in a statement. “By buying later, Trump is spending more per ad buy and getting worse ad placements, particularly for high-viewership programming like live sports.”

More numbers from AdImpact show Democrats have outspent Republicans in every battleground state since July 22, with Pennsylvania receiving the largest share of presidential ad spend, followed by Michigan then Georgia.

The latest national figures from poll aggregator 538 place Harris ahead of Trump by a slim margin, 48.5% to 45.9%.