The seven political races billionaire environmentalist Tom Steyer has picked to play in this year are instructive not only for those he has chosen but also for those he has ignored.

As The Wall Street Journal reported Thursday, Mr. Steyer has pledged at least $50 million of his own money for a $100 million effort to boost the candidacies of Democrats running for the Senate in Colorado, New Hampshire, Iowa and Michigan and for governor in Florida, Maine and Pennsylvania.