Internal documents from the Environmental Protection Agency indicate staff members believed Administrator Stephen Johnson might have to consider resigning if he turned down California's request to reduce vehicle greenhouse gas emissions.

Johnson denied the waiver request in December, blocking California and at least 16 other states from implementing the reductions.

Democratic Sen. Barbara Boxer of California, who is investigating the decision, released new transcripts from internal EPA documents Tuesday.

Among them is a staff memo prepared for a senior official in the air quality division to present to Johnson. It urged Johnson to grant the waiver or find a compromise. The memo warns Johnson that he "has to find a way to get this done," adding that if he could not, he would face a decision about whether to step down.