Less than two hours later, Representative Mikie Sherrill, the Democratic candidate for governor of New Jersey, seized on the decision. She promised to “fight this tooth-and-nail and sue the Trump administration,” and contrasted herself with her Republican opponent, Jack Ciattarelli, who she said had pledged to never take the Trump administration to court. (Mr. Ciattarelli has said his attorney general would not sue President Trump over executive orders, though not if he would sue over Gateway.)