During a hearing on the State Department’s 2015 budget, Ms. Landrieu, a Democrat who has been a strong pipeline proponent and faces a tough re-election fight this year, pressed Mr. Kerry to approve the project, which would carry crude from Canada’s oil sands and from North Dakota’s Bakken Shale Formation to Gulf Coast refineries. Ms. Landrieu, the new chairwoman of the Senate Energy Committee, said, “Canada is our closest, strongest trading partner,” and “a majority of American people” support Keystone. “It is hard for me to understand why there are still questions about whether building this pipeline is in our...