WASHINGTON — President-elect Donald Trump and President Obama don’t agree on much, but they do have one thing in common: Both say that marijuana legalization should be left to the states.

“In terms of marijuana and legalization, I think that should be a state issue, state by state,” Trump said at a campaign event in Nevada last year.

But many pot backers worry that Trump is unpredictable and could easily change his mind, particularly if he appoints a legalization opponent such as New Jersey Republican Gov. Chris Christie or Republican former New York Mayor Rudy Giuliani as his attorney general.

As a result, legalization supporters say they’ll be ready to apply pressure to make sure Trump keeps his word when he moves to the White House on Jan. 20.

“Reversing course and going against the tide of history would present huge political problems that the new administration does not need,” said Tom Angell, chairman of the pro-legalization group Marijuana Majority.

Along with Trump, pot emerged as the big winner Tuesday. Voters doubled the number of states that allow recreational use of marijuana, with California, Nevada, Massachusetts and Maine joining the list that already comprised Washington, Colorado, Alaska and Oregon.

At the same time, voters in Florida, North Dakota and Arkansas approved marijuana for medical use, while Montana residents voted to loosen restrictions on the state’s medical marijuana laws. They’ll be added to the list of 25 states that had voted earlier to allow using pot for medical reasons.

Legalization supporters lost in only one state, Arizona, where voters rejected a plan to tax and sell marijuana to adults.

Winning “eight out of nine is a shocking track record of success,” said Rob Kampia, executive director of the Marijuana Policy Project, another pro-legalization group. Kampia was especially pleased with the outcome in Nevada, saying “the third time was a charm” after voters had rejected legalization in 2002 and 2006.

Oregon Democratic Rep. Earl Blumenauer, one of the top backers of legalization in Congress, said the new administration “is going to inherit a landscape unlike any in our history” and predicted that Trump will not interfere with states. He said the new president would have difficulty trying to intervene anyway, with polls showing a strong majority of Americans favor ending federal prohibition of the drug.

“Even if we didn’t have signals from Donald Trump, the fact is that this is where the public has moved,” said Blumenauer, who first promoted legalization as a member of the Oregon Legislature in 1973. “It’s not been the politicians who’ve led on this.”

Kevin Sabet, president of the anti-legalization group Smart Approaches to Marijuana, called the election results disappointing but “not wholly unsurprising” since legalization backers had spent more money than opponents.

“We will redouble our efforts with this new Congress,” Sabet said Trump’s track record remains a worry for many legalization supporters. He told a conservative gathering last year that Colorado had experienced “big problems” by legalizing pot: “I think it’s bad and I feel strongly about that.”