Source: https://www.fec.gov/data/spending-bythenumbers/
Inflation Adjusted Data Over Time
Overall, both parties have increased their spending over time when the data is adjusted for inflation. This data is spending for all candidates, which includes primary contenders. For the 20 election years Democrats have outspend Republicans in 11 while Republicans have outspend Democrats in 9. Notably, relative spend for a party seems to rise when the sitting president is of the other party.
