Arbitrage is the practice of taking advantage of different prices of an asset in different markets, buying in one and immediately selling in the other. In particular, Steyer learned at Goldman Sachs the practice of merger arbitrage, in which he would simultaneously buy and sell the stocks of two companies that are merging, and profit when the deal closed. Investors reportedly liked Steyer because he got great returns with relatively low-risk strategies like that one; unlike many in his generation of financiers, he didn’t get rich borrowing money and taking huge risks. He got rich studying systems carefully and exploiting the gaps.

And that’s what Steyer’s doing on that debate stage, his spokesman circulating the press file looking like the cat the swallowed the canary. It’s why moderator Wolf Blitzer is asking — aren’t we all — “Would a President Steyer use military force as a deterrent?”

Some of the candidates who aren’t there also raised and spent millions. But only Steyer exploited the DNC’s complex system, in which you need to meet percentage requirements in a series of polls to qualify for the debates.