According to this morning’s New York Times, former New York Mayor Michael Bloomberg has decided that there are not enough billionaires trying to sway the outcome of the next presidential election: “If Republicans were to nominate Mr. Trump or Senator Ted Cruz of Texas, a hard-line conservative, and Democrats were to pick Mr. Sanders, Mr. Bloomberg—who changed his party affiliation to independent in 2007—has told allies he would be likely to run.”

The way the sentence is worded, it sounds like Bloomberg is equally opposed to outcomes he doesn’t like on the Republican (Trump/Cruz) and Democratic (Sanders) side. But as a practical matter, Bloomberg’s entering the race would almost certainly throw it to the Republicans. Trump or Cruz would get the hardcore GOP partisan vote, while well-to-do but social liberals would desert the Democrats for Bloomberg. Hillary Clinton supporter Neera Tanden, of the Center for American Progress, laid out the logic clearly on Twitter:

If Sanders wins Dem nomination, it's not likely Sanders v. Trump.It's likely to be Sanders v. Bloomberg v. Trump 1/2 https://t.co/Rhn6uJvAbi — Neera Tanden (@neeratanden) January 23, 2016

Perhaps Dems in nominating states should think of what will happen in Sanders v. Bloomberg v. Trump. And how likely we get a Pres. Trump 2/2 — Neera Tanden (@neeratanden) January 23, 2016

Bloomberg’s intent is clear: He’s considering running not because he has a viable program he wants to promote, but because he wants to exercise a veto over the already existing parties—especially a veto over whom the Democrats pick. His gambit makes Sanders’s path to the White House much more difficult but also explains why Sanders’s campaign is necessary.