PHOENIX — Rep. Ron DeSantis rode a robust endorsement from President Donald Trump to victory Tuesday in Florida's Republican gubernatorial primary. DeSantis was one of several Republicans running in contests in Florida and Arizona who hoped that cozying up to the president would be rewarded by voters.

The winner of the Florida governor's race will give his or her party an advantage in a key political battleground heading into the 2020 presidential campaign. The Democratic primary featured a crowded and diverse crowd, and it was too early to call a winner as polls closed across the state. Former Rep. Gwen Graham, who would be the state's first female governor, and former Tallahassee Mayor Andrew Gillum, who would be the state's first black governor, were locked in a tight race.

Trump cheered DeSantis' victory on Twitter Tuesday night, writing: "Ron will be a fantastic Governor. On to November!"

Florida Gov. Rick Scott is vacating the governor's mansion to run for Senate. He easily won his primary, setting up a showdown with Democratic Sen. Bill Nelson that is expected to be one of the nation's most competitive races.

In Arizona, primary contests were shadowed by the death of Sen. John McCain. Though McCain was a towering figure who was elected to the Senate by Arizonans six times, the three Republican candidates running to replace his retiring seat-mate, Sen. Jeff Flake, aligned themselves more with the president than the longtime senator.

Arizona Gov. Doug Ducey planned to name a replacement to fill McCain's seat after the primary.

In the state's largest county, dozens of polling locations didn't open on time and voters reported being turned away. Leaders in Maricopa County rejected calls to try to keep polls open later, saying it may confuse voters and delay returns. No problems were reported elsewhere in the state.

Voting was also underway in Oklahoma, where two GOP candidates in a runoff race for governor have been battling over who is more supportive of Trump.

Trump surprised Florida Republicans late last year with his endorsement of DeSantis, and frequently tweeted about the lawmaker, one of his staunchest supporters in Washington. His backing helped push DeSantis past Agriculture Commissioner Adam Putnam, who has held elected office in Florida since 1996, quickly built up establishment support and raised millions of dollars.

The Democratic gubernatorial field in Florida was the most crowded since 1978. Graham, who was hoping to claim the office once held by her father, Bob Graham, had been polling favorably leading up to the primary.

Gillum, a favorite of progressives, spent the least of the five major Democratic candidates and had the smallest television presence. He often said he was the only candidate in the race who wasn't a millionaire or billionaire, and won the endorsement of Vermont Sen. Bernie Sanders.

Democrats also eyed pickup opportunities in Florida as they try to flip control of the U.S. House. One of their best chances is in South Florida, where Republican Rep. Ileana Ros-Lehtinen is retiring in a district that should favor Democrats.

Nine Democrats were vying to succeed Ros-Lehtinen, including Donna Shalala, who served as President Bill Clinton's Health and Human Services secretary.

The contests in both Florida and Arizona were being closely watched for signs of how the political battlegrounds might tilt in the 2020 presidential election.

McCain's death has highlighted anew the shift in the Republican Party since he captured the GOP nomination for president in 2008. With his consistently conservative voting record, Arizonans elected McCain to the Senate six times, including in 2016. But his more moderate stance on immigration and his deciding vote last year against Trump's efforts to repeal President Barack Obama's health care law turned off many GOP voters.

A CNN survey in June found that 67 percent of Democrats had a favorable opinion of McCain, while just 33 percent of Republicans did.

Among those on the Arizona ballot was former state Sen. Kelli Ward, who tried unsuccessfully to unseat McCain in 2016. When McCain's family said last week that he was discontinuing medical treatment, Ward speculated in a later-deleted Facebook post that the announcement was intended to hurt her campaign for Flake's seat.

Ward apologized Monday, saying she was bemoaning media coverage rather than the family's announcement.

"I do understand how many could have misconstrued my comments as insensitive, and for this I apologize," Ward said.

Also running for the Senate nomination was former Maricopa County Sheriff Joe Arpaio, the controversial immigration hardliner. Trump spared Arpaio a possible jail sentence last year by pardoning his federal conviction stemming from immigration patrols.

McSally, a fighter pilot turned congresswoman in the McCain mold, was hoping Ward and Arpaio split Arizona's anti-establishment vote.

The winner of the GOP primary is likely to face Democratic Rep. Kyrsten Sinema, who had only token primary opposition. Sinema announced that she was pausing her campaign Wednesday and Thursday, when McCain's body will lie in Arizona's Capitol.

Sinema's and McSally's Senate runs also have created House openings in Arizona, a fast-growing and increasingly diverse state where Democrats are eager to gain a foothold. McSally's district in particular is expected to be one of the most competitive House races in November's general election.

Pace reported from Washington. Associated Press writers Brendan Farrington and Gary Fineout in Tallahassee, Florida, Sean Murphy in Oklahoma City, AP polling editor Emily Swanson in Washington, Kelli Kennedy in Miami and Freida Frisaro in Fort Lauderdale contributed to this report.

AP