Charlie Crist will challenge Florida’s Republican governor, Ron DeSantis, in November after trouncing Nikki Fried, the state agriculture commissioner, in Tuesday’s Democratic primary.

Crist, a former Republican governor of Florida who switched parties and became a Democratic congressman, fought a campaign touting his experience in office and opposition to the 15-week abortion ban signed by DeSantis.

In his victory speech in St Petersburg, Crist promised that if elected he will on his first day in office sign an executive order overturing the abortion law.

And he pledged to end the White House hopes of “wannabe dictator” DeSantis, who is tipped as a likely contender for the Republican presidential nomination in 2024. DeSantis has signed a raft of culture war legislation in Florida, attacking LBGTQ+ rights and “woke” corporations.

“Our fundamental freedoms are literally on the ballot,” Crist said. “A woman’s right to choose on the ballot. Democracy on the ballot. Your rights as minorities are on this ballot.

“That’s what’s at stake in this election, make no mistake about it, because this guy wants to be president of the United States of America and everybody knows it.

“However, when we defeat him on 8 November, that show is over.”

With fewer than 15% of votes left to count, Crist held a commanding lead over Fried, a progressive and the only statewide elected Democrat currently in office, by roughly 60% to 35%. But turnout, particularly in central Florida, was far below that of four years ago, a lack of enthusiasm among Democrats one of the main fears of party officials.

In his final pre-election press conference, Crist said he planned to appear at a “unity rally” with his beaten opponent in south Florida later in the week.

Their focus will switch to ousting DeSantis, whom Crist has branded Florida’s “absentee” governor for constantly attacking Joe Biden’s policies and appearing to concentrate on out-of-state fundraising for a national campaign rather than problems at home.

“He’s campaigning this last weekend in New Mexico, Ohio, Pennsylvania, and I think another state, but he’s been doing that for a year, maybe more,” Crist said.

“We have issues here the governor ought to be dealing with, the housing crisis, we pay our teachers 48 or 49 of 50 states, that’s embarrassing.

“And the fact he already has taken away a woman’s right to choose with the law that he signed, the 15-week law that has no exceptions for rape or incest, is barbaric.”

During her campaign, Fried attacked Crist’s Republican roots and perceived flip-flops over abortion, and painted herself as the only candidate capable of beating DeSantis. Crist, who ran unsuccessfully for the Senate in 2010, has the unenviable distinction of losing statewide races as a Republican, Democrat and independent.

But he appears to have been more popular with women voters in this primary, and pointed out that, when he was governor 12 years ago, he vetoed an anti-abortion bill.

On Tuesday night, Fried told NBC News she would accept if Crist asked her to be his running mate.

“I’ve said to Charlie, both tonight and throughout this entire election, that my No 1 priority is making sure that we make Ron DeSantis a one-term governor and not eligible to run for president of the United States in 2024.

“Ron DeSantis is our greatest threat to democracy, so I will do everything in my power, including being on Charlie’s ticket, to make sure that happens in November.

“What we did here in this election, is we created a movement for women across the state of Florida. We gave inspiration, we gave motivation, and so whatever it takes to make sure that Ron DeSantis is defeated in November – I’m all in.”

DeSantis won the 2018 election against the Democratic challenger, Andrew Gillum, by barely 30,000 votes, or 0.4% of 8.2m cast. But toppling him in November will be a formidable task as Florida has trended increasingly Republican in recent years.

The incumbent also has a war chest in excess of $100m, far above what Crist has been able to raise. Even so, Crist remains confident he can win on the issues.

“Today the people of Florida clearly sent a message,” he said. “They want a governor who cares about them to solve real problems, who preserves our freedom, not a bully who divides us and takes our freedom away.”

In another much-watched Democratic primary, Val Demings, a congresswoman and former Orlando police chief, easily secured the nomination to challenge the Republican US senator Marco Rubio in November.

Rubio’s seat is one of several targeted by Democrats as they attempt to build a majority in the 50-50 chamber and negate their reliance on Vice-president Kamala Harris’s tiebreaking vote.

A competitive and crowded Democratic primary for the House seat Demings vacated went to Maxwell Frost, a 25-year-old progressive endorsed by the Massachusetts senator Elizabeth Warren and Pramila Jayapal, a leading House progressive from Washington state.

In a tight Republican primary for another central Florida House seat, the far-right extremist Laura Loomer, a self-declared Islamophobe, election denier and conspiracy theorist, narrowly lost to the incumbent, Dan Webster.