Searching the onscreen text of CNN, MSNBC and Fox News thus far in 2020, it is possible to scan for all airtime containing the phrase "Paid for by Donald J. Trump for President, Inc." which is the concluding text on at least some of his official campaign ads. The resulting hourly timeline below shows that his ads are fairly well spread throughout the day, with only around two hours in the morning EST without ads. There is also a highly visible "reset" period for a few days at the end of July and early August where no ads were run. His heaviest buys have come on Fox News, followed by CNN and MSNBC.