Outside spending is not spread evenly across the map. It pours into a handful of races and ignores the rest. Of the 104 U.S. Senate races held in 2020, 2022 and 2024, fewer than half drew even $1 million of it, and 42 drew almost none at all.
So the interesting question is not whether outside money is large. It is what happens in the races where it shows up. For each candidate we can add the independent expenditures spent supporting them to the independent expenditures spent attacking their opponent — the money spent trying to put them in office — and set it against the result.
The answer is that it buys close to a coin flip. Across the 48 Senate races with at least $1 million of outside money, the candidate with more of it behind them lost 20 times. Among the most expensive races the pattern holds: in the 31 races drawing $25 million or more, the better-funded candidate lost 17 of them. The correlation between a candidate's share of the outside money and their margin of victory is +0.08 — statistically indistinguishable from zero.
Some of the largest sums in modern politics bought nothing. In Georgia in 2020, David Perdue had $171.9 million behind him to Jon Ossoff's $94.1 million, and lost. In North Carolina the same year, Cal Cunningham held a narrow money advantage over Thom Tillis and lost. In 2024, $865.7 million stood behind Kamala Harris to Donald Trump's $793.8 million.