After repeatedly seeking to discredit mail-in voting, President Donald Trump on Tuesday claimed Florida's election system is "safe and secure" and encourages Floridians to vote by mail.

Trump's change in attitude over the swing state's use of mail-in ballots undermines an argument he'd maintained throughout the coronavirus pandemic -- that mail-in ballots pose a distinct election security risk that absentee ballots do not. But elections experts have repeatedly underscored that mail-in voting and absentee voting are essentially the same thing, and that there are strict measures in place to verify the authenticity of all ballots cast by mail.

"Whether you call it Vote by Mail or Absentee Voting, in Florida the election system is Safe and Secure, Tried and True. Florida's Voting system has been cleaned up (we defeated Democrats attempts at change), so in Florida I encourage all to request a Ballot & Vote by Mail! #MAGA," he tweeted.

When asked about the reversal later Tuesday afternoon, Trump seemed to imply that Republican-run states with existing mail-in voting programs were up-to-par, but Democratic states establishing or expanding mail-in voting during the pandemic were not.

"So Florida's got a great Republican governor and it had a great Republican governor (before that) ... and over a long period of time they've been able to get the absentee ballots done extremely professionally. Florida's different from other states," Trump said, before criticizing vote-by-mail efforts in Nevada and New York, states led by Democratic governors.

The President has recently begun laying the groundwork for the doubt and suspicion he could cast on election results if counting mail-in ballots -- which are expected to be more widely used as a result of the pandemic -- ultimately delays the declaration of a winner.

He also floated delaying the election in a tweet last week that received bipartisan condemnation. The President does not have the power to do this -- Congress does.

There is no evidence mail-in voting leads to widespread fraud. But the assertion was notable because it is an effort to sow doubt about the legitimacy about the election, now 91 days away.

"I want to have the election. But I also don't want to have to wait for three months and then find out that the ballots are all missing and the election doesn't mean anything. That's what's going to happen," Trump said at a Thursday news conference, during which he also called vote-by-mail a "disaster" and argued people should have to cast their votes in person.

Asked about the mixed messages, White House press secretary Kayleigh McEnany said: "Well the President's always said that absentee voting for a reason is different than mass mail-out voting like what Nevada is seeking to do, which leads to mass fraud."

Again, there's no evidence of widespread fraud with mail-in voting.

A Trump campaign official confirmed that the Florida victory McEnany and Trump referred to was a recently dropped lawsuit over the state's voting laws. Priorities USA and other left-leaning groups sued Florida Gov. Ron DeSantis and the Republican Party in an effort to change Florida voting laws, citing the coronavirus pandemic.

Meanwhile, the President's team is fighting to preserve aspects of mail-in voting they hope will offer Trump a strategic advantage. That has included a push in various states for policies such as enhanced signature matching, requirements for people to file an application before they receive a ballot and limits to when and where mail-in ballots will be counted -- things election experts have said could lead to fewer votes being counted from groups that skew Democratic.

Some administration officials and Republican allies have expressed frustration at Trump's rhetoric questioning the validity of mail-in voting behind closed doors -- acknowledging that it will likely be necessary and perhaps even helpful for the President in some places.

In Florida, a recent CNN/SSRS poll found 59% of Democratic-leaning voters would rather cast mail ballots in the election versus 21% of Republican-leaning voters.

A senior Republican aide told CNN that Florida Republicans had been pressing the President to endorse the state's vote-by-mail system and assuring him that the practice was safe.

The aide said high vote-by-mail turnout is a key to Republicans winning in November and there was concern among GOP officials in the state that Trump's attacks on the practice would damage their hopes in the fall.

Trump's reversal comes days after Florida Republican Sen. Marco Rubio said on a Trump campaign conference call that he had "no concerns" about mail-in voting in his state.

"We've been doing it a long time. I can't speak for every state, I mean there are some states that are automatically mailing everybody a ballot, but our system is well established, it's been used for a long time, we've frankly never had issues with it, generally speaking," Rubio told reporters at the Capitol Tuesday.

Asked if he was the concerned the President's rhetoric about mail-in voting will discourage his constituents, Rubio said: "I don't think it will discourage them from voting. I know they might just end up voting on election day. That's what we saw in 2016."

CNN's Jeremy Herb, Pam Brown, Sarah Westwood, Kristen Holmes Ryan Nobles and Maegan Vazquez contributed to this report.