Elections are expensive, and this year's will be the most expensive US midterm elections ever, costing nearly $4 billion. This graphic, based on data from Open Secrets, highlights some of the costliest individual Senate and House races:
According to represent.us, the higher-spending campaign wins 91 percent of the time. That's in part because incumbents tend both to raise more money and to have high reelection rates themselves.
This chart, using the data from the Federal Election Commission (FEC) and represent.us, shows how money affects a candidate's odds of winning:
These numbers count House and Senate elections but not gubernatorial races, and they don't account for money that hasn't been reported to the FEC, leaving out third-party "issue ad" spending, which makes up a significant portion of independent campaign spending.
Of course, money isn't the sole determinant of electoral outcomes. For example, races where a very weak, underfunded challenger loses to a much better financed, more popular incumbent contribute to the figure, but don't really represent a triumph of money so much as they reflect the state or district's underlying politics, and the popularity of the incumbent.