LAS VEGAS, Nevada — Joe Biden said he differs from his Democratic 2020 rivals by not backing the legalization of marijuana, saying the scientific community doesn’t know enough about whether it serves as a “gateway drug” to more dangerous substances.

“The truth of the matter is, there’s not nearly been enough evidence that has been acquired as to whether or not it is a gateway drug,” the former vice president said in Las Vegas on Saturday at a campaign event. “It’s a debate, and I want a lot more [information] before I legalize it nationally. I want to make sure we know a lot more about the science behind it.”