WASHINGTON — Democrats hold double-digit leads in the U.S. Senate contests in Arizona and Ohio, while it’s much closer in Florida, according to a trio of NBC News/Marist polls from these three key states in November’s midterm elections.

In Arizona, Democrat Rep. Kyrsten Sinema is ahead of all three potential Republican opponents — Kelli Ward by 10 points among registered voters (48 percent to 38 percent), Rep. Martha McSally by 11 points (49 percent to 38 percent) and Joe Arpaio by 25 points (57 percent to 32 percent).

In Ohio, Sen. Sherrod Brown, a Democrat, leads GOP challenger Jim Renacci by 13 points, 51 percent to 38 percent.

But in Florida, the incumbent Democrat, Sen. Bill Nelson, gets support from 49 percent of registered voters, while his Republican challenger, Gov. Rick Scott, is at 45 percent — a result that’s within the poll’s margin of error.

Other polling has found this Florida Senate race competitive, with some surveys showing Scott ahead and others with Nelson leading.

A “wide open” GOP primary race in Arizona

The NBC/Marist poll of Arizona finds that the contest for the GOP Senate nomination is tight, with 30 percent of Republican voters backing McSally; 28 percent behind Ward, a former state senator; and 21 percent supporting Arpaio, the former sheriff.

Twenty-one percent say they’re undecided. The primary is Aug. 28.

“This primary contest is wide open,” said Lee Miringoff, the director of the Marist College Institute for Public Opinion, which conducted the three state polls for NBC News. “More than one-in-five potential GOP voters are undecided, and the total proportion of persuadable voters in this contest reaches 41 percent when those who might change their mind about their current choice are included,” he said.

Nearly half of Democrats are undecided in Florida’s gubernatorial race

Meanwhile, in Florida, Miami Beach Mayor Philip Levine (at 19 percent) and former Congresswoman Gwen Graham (at 17 percent) lead the pack in the Democratic primary for Florida governor, according to the NBC/Marist poll of that state.

Tallahassee Mayor Andrew Gillum is at 8 percent, and no other Democrat gets more than 4 percent.

A whopping 47 percent of Florida Democrats say they’re undecided.

In the GOP race to succeed Scott, who is term limited, state Agriculture Commissioner Adam Putman gets support from 38 percent of Republican voters, while Rep. Ron DeSantis gets 21 percent.

President Donald Trump has endorsed DeSantis.

A combined 42 percent of GOP voters say they’re undecided or supporting another candidate.

GOP leads by 4 points in Ohio governor's race

And in Ohio’s contest for governor, Republican Mike DeWine holds a 4-point lead over Democrat Richard Cordray among registered voters, 46 percent to 42 percent, which is within the poll’s margin of error.

Eleven percent are undecided.

More numbers from the NBC/Marist polls of Arizona, Florida and Ohio will be released on Wednesday.

The NBC News/Marist poll of Arizona was conducted June 17-21 of 839 registered voters (which has a margin of error of plus-minus 4.5 percentage points) and 371 Republican primary voters (plus-minus 6.7 percentage points.

The NBC News/Marist poll of Florida was conducted June 17-21 of 947 registered voters (plus-minus 3.9 percentage points), 344 registered Democrats (plus-minus 6.5 percentage points) and 326 Republicans (plus-minus 6.7 percentage points).

The NBC News/Marist poll of Ohio was conducted June 17-22 of 778 registered voters (plus-minus 4.4 percentage points). All three live-caller polls interviewed respondents by landline and cellphone.