The conventional wisdom among Donald Trump’s supporters is that his success doesn’t rely much on political ads. The evidence suggests otherwise. As Trump’s ad spending has risen, the race has tightened. As it has dipped, his polling deficit has widened.

Over the past three months, according to the Associated Press’s week-by-week tallies, Hillary Clinton has outspent Trump on television and radio ads by a total of $155 million to $19 million. Rounding to the nearest whole number, that’s a ratio of 8-to-1.