Republicans and their allies are running approximately $500 million behind Democrats in ad spending running from August until election day, according to a new report.

Democratic campaigns and outside groups supporting them have spent $1.8 billion on ads set to air between August 1 and November 5 as of September 20, according to Axios’ analysis of data from the analytics firm AdImpact. Republicans and the groups backing their campaigns, meanwhile, have paid about $1.3 billion for ad space over the same period.

The data includes spending on presidential, congressional and down-ballot races, according to Axios.

Republican leadership, publicly and privately, had expressed grave concern over the financial lead the Democrats have built moving towards election day.

“Right now, the left-wing billionaires are massively outspending us,” Republican Montana Sen. and National Republican Senatorial Committee Chair Steve Daines said in his July address to the Republican National Convention. “That’s what’s keeping me up at night.”

Daines ended his speech by imploring his audience to visit a Republican fundraising website and donate to help the party’s effort to retake the Senate.

Leaders of the Congressional Leadership Fund and the National Republican Congressional Committee (NRSC), groups responsible for helping conservatives win House races, have privately warned party leaders that they are tens of millions of dollars behind Democrats in key battleground races.

“Money can’t buy you love, but it can influence the outcome of an election,” NRSC executive director Jason Thielman previously told the Daily Caller News Foundation.

“The only thing preventing us from having a great night in November is the massive financial disparity our party currently faces,” he continued. “We are on a trajectory to win the majority, but unless something changes drastically in the next six weeks, we will lose winnable seats.”

As of early August, Democrats were outspending Republicans in virtually every competitive Senate race, including Montana. Republican nominee Tim Sheehy, however, leads Democratic incumbent Sen. Jon Tester by over five points in Real Clear Polling’s average of polls as of Sept. 23.

Control of the Senate could come down to which party wins in Montana.

Record amounts of dark money, funds with an untraceable original source, have flooded the 2024 election, according to a report published by OpenSecrets. One Democratic-aligned dark money group, the Sixteen Thirty Fund, has historically received a large portion of its funding from Swiss billionaire Hansjorg Wyss.