Florida is one of a number of GOP-leaning states, most notably Georgia, to enact voting changes in light of the 2020 election.
"The 2020 election was one of the most secure elections in American history. There’s no legitimate reason to change the rules right now to make it harder to vote. That’s built on a lie," deputy press secretary Karine Jean-Pierre told reporters aboard Air Force One.
"The only reason to change the rules right now is if you don’t like who voted, and that should be out of bounds," she said.
"There’s some states with bad laws trying to make them good. And some states with good laws trying to make them even better. That’s moving forward. Florida is moving in the wrong direction," the press secretary continued.
She reiterated support for HR 1, the House-passed sweeping voting rights bill, saying it is needed to make sure elections are "secure and convenient."
De Santis signed the bill live on "Fox & Friends."
"I have what we think is the strongest election integrity measures in the country," DeSantis said. "We're making sure we're enforcing voter ID … We're also banning ballot harvesting. We're not gonna let political operatives go and get satchels of votes to dump them in some drop box."
The bill allows drop boxes but with restrictions.
"Drop boxes must be geographically located so as to provide all voters in the county with an equal opportunity to cast a ballot," the bill says, and "must be monitored in person."
DeSantis said he is "not a fan" of drop boxes but that the legislature "wanted to keep them." So the new law, DeSantis said, "The drop boxes will be available only when they're monitored and during regular voting hours."
DeSantis added: "We're also prohibiting mass mailing of balloting. We've had absentee voting in Florida for a long time. You request the ballot. You get it. And you mail it in. But to just indiscriminately send them out is not a recipe for success."
Also among its provisions is a "prohibition on the use of private funds for election-related expenses," which is a response to the fact Facebook CEO Mark Zuckerberg and others provided funding to some states and cities last year to help run the election.
Those groups said their goal was simply to help increase voter turnout and assist stressed government agencies. But some Republicans said the funding was targeted at blue areas, therefore potentially favoring Democrats.
Democrats, meanwhile, have slammed the Florida bill and similar efforts in other states as "voter suppression." Others have said the legislatures that are moving ahead with new bills targeted at election security are doing so based on the falsehood that the 2020 presidential election saw widespread fraud. DeSantis has touted the security of the 2020 election in his state, where President Trump won the vote, but said more needs to be done for the future.
Fox News' Tyler Olson contributed to this report.