The president’s apparent willingness to veto a bipartisan bill to approve the Keystone pipeline seems to me, politically, to be a clarifying moment. Obama says that the pipeline would create a trivial number of jobs. The potential environmental impact of the pipeline seems far more trivial. Yet it’s enough for him to flout public opinion, discard those jobs, and break with a significant number of congressional Democrats. He has set up an early veto fight with the Republican Congress that does not seem to me to be helpful to himself, his party, or his party’s nominee to be his successor. Hillary Clinton will have to choose whether to side with environmental groups, many of the party’s top donors, and President Obama, or the public, some unions, and Democrats including her husband. How she chooses will be a statement about the contemporary Democratic party’s priorities, which makes it a bigger issue than its merits might suggest.