Floor manager for the pending highway bill Sen. Barbara BoxerBarbara Levy BoxerOnly four Dem senators have endorsed 2020 candidates Hispanic civil rights icon endorses Harris for president California AG Becerra included in Bloomberg 50 list MORE (D-Calif.) led the opposition that resulted in the 46-52 defeat, arguing the amendment had the potential of ruining America's pristine coastlines and the tourism industry that depends on them. 

"This is an antijobs amendment that threatens our coastal economies ... where the coasts are an engine of economic growth," Boxer said.

"This is a giveaway to big oil," she added. 

But in floor debate earlier in the day, Vitter argued for expanded drilling opportunities, arguing that high gas prices are stunting economic growth.

“[This] is the single biggest step we can take right now to try to rein in spiraling gas prices,” Vitter said.