When you want information about campaign spending, the place to turn is the Open Secrets website run by the Center for Responsive Politics.
It will take a few weeks longer to get a final tally on campaign spending for the 2020 elections, but some patterns are already pretty clear, as they point out in "2020 election to cost $14 billion, blowing away spending records" (October 28, 2020). They write:
The 2020 election is more than twice as expensive as the runner up, the 2016 election. In fact, this year’s election will see more spending than the previous two presidential election cycles combined.
The massive numbers are headlined by unprecedented spending in the presidential contest, which is expected to see $6.6 billion in total spending alone. That’s up from around $2.4 billion in the 2016 race.
Democratic presidential nominee Joe Biden will be the first candidate in history to raise $1 billion from donors. His campaign brought in a record-breaking $938 million through Oct. 14, riding Democrats’ enthusiasm to defeat Trump. President Donald Trump raised $596 million, which would be a strong fundraising effort if not for Biden’s immense haul. ...
Spending by deep-pocketed national groups also is driving the total cost of election higher. In the month of October alone, outside spending by super PACs and other big-money groups totaled nearly $1.2 billion. These groups are spending far more to boost Biden than help Trump, further aiding the Democrats cash-flush campaign. ...
Democratic candidates and groups have spent $6.9 billion, compared to $3.8 billion for Republicans. Democrats' spending falls to $5.5 billion when excluding spending by billionaire presidential candidates Michael Bloomberg and Tom Steyer.
The article and website are full of interesting illustrative figures. For example, here's total spending for the last few presidential years, divided into spending on the presidential and congressional campaigns.
Here's campaign spending broken down by the sources of funds.
And here's campaign spending from different industries, divided into Ds and Rs.
Finally, there's an irony worth noting here. It's more common for Democrats than for Republicans to express concern over high levels of campaign spending, and to suggest ways of limiting it. But if Joe Biden ends up prevailing when all the election counts are said and done, as seems likely, the enormous edge in campaign spending for Biden and Democratic candidates overall may well have made the difference in the key states Biden needed to win.
Timothy Taylor is an American economist. He is managing editor of the Journal of Economic Perspectives, a quarterly academic journal produced at Macalester College and published by the American Economic Association. Taylor received his Bachelor of Arts degree from Haverford College and a master's degree in economics from Stanford University. At Stanford, he was winner of the award for excellent teaching in a large class (more than 30 students) given by the Associated Students of Stanford University. At Minnesota, he was named a Distinguished Lecturer by the Department of Economics and voted Teacher of the Year by the master's degree students at the Hubert H. Humphrey Institute of Public Affairs. Taylor has been a guest speaker for groups of teachers of high school economics, visiting diplomats from eastern Europe, talk-radio shows, and community groups. From 1989 to 1997, Professor Taylor wrote an economics opinion column for the San Jose Mercury-News. He has published multiple lectures on economics through The Teaching Company. With Rudolph Penner and Isabel Sawhill, he is co-author of Updating America's Social Contract (2000), whose first chapter provided an early radical centrist perspective, "An Agenda for the Radical Middle". Taylor is also the author of The Instant Economist: Everything You Need to Know About How the Economy Works, published by the Penguin Group in 2012. The fourth edition of Taylor's Principles of Economics textbook was published by Textbook Media in 2017.