- Three NBC News/Marist polls of key Senate contests show a tight race in Florida and comfortable leads for Democrats in Arizona and Ohio.
- Vulnerable incumbent Democratic Sen. Bill Nelson has a 4-percentage point edge over GOP Gov. Rick Scott.
- Democratic Rep. Kyrsten Sinema leads all of her potential Republican opponents in Arizona by double digits.
- Democratic Sen. Sherrod Brown also holds a double-digit edge of GOP Rep. Jim Renacci.
An expensive and closely watched Senate race in battleground Florida is tight, while Democrats hold solid leads in their bids to take or hold seats in Arizona and Ohio, according to three NBC News/Marist polls released Tuesday.
All three races will play a major role in whether Republicans can keep or expand their 51 seat to 49 seat majority in the chamber after November's midterm elections. The races will help to determine which policies the Senate pursues next year and whether President Donald Trump can keep up his flurry of conservative judicial appointments.
In Florida, incumbent Democratic Sen. Bill Nelson garners 49 percent of support among registered voters, versus 45 percent for Republican Gov. Rick Scott, an NBC/Marist survey says. The race, one of 10 this year where a Democrat defends a seat in a state Trump won in 2016, has already attracted a whopping $9 million in outside spending, according to the Federal Election Commission.
Democrats face a daunting Senate map, as the party's senators and independents who caucus with them defend 26 seats. Only nine Republican-held spots in the Senate are up for grabs.
Democrats have perhaps their best chance to flip a seat in Arizona, a state Trump won by about 4 percentage points in 2016. Sen. Jeff Flake, R-Ariz., will not run for re-election there.
The likely Democratic nominee, U.S. Rep. Kyrsten Sinema, holds a double-digit lead over all of her potential opponents, according to an NBC/Marist poll. In a hypothetical contest with Rep. Martha McSally, Sinema gets 49 percent of support among registered voters, compared with 38 percent for the Republican candidate.
The Democratic representative has a 10-percentage point edge — 48 percent to 38 percent — over physician and former state legislator Kelli Ward. Sinema's lead balloons to 25 percentage points — 57 percent to 32 percent — against former Maricopa County Sheriff Joe Arpaio.
The race for the GOP nomination appears tight ahead of the August 28 primary. McSally garners 30 percent of support among the potential Republican electorate, compared with 28 percent for Ward and 21 percent for Arpaio, according to the poll.
In Ohio, incumbent Democratic Sen. Sherrod Brown holds a comfortable lead in his race against GOP Rep. Jim Renacci. More than half of respondents, 51 percent, say they would prefer Brown, versus 38 percent for Renacci.
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 cell phone.