Even as GOP presidential nominee Donald Trump has stumbled in the polls, Republican prospects of holding onto the majority in the U.S. Senate have held firm — and in some states are improving.

Sen. Marco Rubio has led in the Florida Senate race in every public poll since June, prompting University of Virginia’s Center for Politics this week to move the contest from “leans Republican” to “likely Republican.”

“Part of that is [Democratic challenger] Patrick Murphy isn’t well-known in a lot of the state. Rubio is very visible.”

Polls by Monmouth and Qunnipiac this week put Ohio Sen. Rob Portman ahead by 15 and 17 percentage points, respectfully, leading gleeful Republicans to declare the race over.

The Democratic Senatorial Campaign Committee has canceled millions of dollars in advertising in both states to focus on other races.

A Quinnipiac poll this week pegged Pennsylvania Sen. Pat Toomey’s lead at 8 points — the first to show him at 50 percent. That race remains volatile, however, with challenger Katie McGinty beating him by 6 points in one poll and tying him in another.

[lz_table title=”Cook Political Report: Senate 2016″ source=””]
|Leans Democrat
Illinois (Kirk)
Wisconsin (Johnson)
|Leans Republican
Arizona (McCain)
Ohio (Portman)
|Toss-up
Nevada (Retiring Democrat)
Florida (Rubio)
Indiana (Retiring Republican)
New Hampshire (Ayotte)
North Carolina (Burr)
Pennsylvania (Toomey)
Missouri (Blunt)
[/lz_table]

With 54 seats in the upper chamber, Republicans can afford to lose only three to guarantee they maintain control. Most experts believe Democratic challengers are heavy favorites to beat incumbent Republicans in Democratic-leaning Illinois and Wisconsin. That would mean Republicans would have to win in three of the four remaining seats where they are most vulnerable, or hold two of those seats and capture the seat of retiring Senate Minority Leader Harry Reid in Nevada.

“That will be very difficult if Trump’s post-debate polling deficit doesn’t improve,” Center for Politics Director Larry Sabato and two others wrote in an update this week.

Back when Rubio was running for president, he had announced plans to retire from his Senate seat whether he won the nomination for president or not, making his seat an attractive target for Democrats. But he changed his mind and has taken control of the race despite expectations that losing his home state to Trump in the presidential primary would damage him.

“The polling hasn’t reflected that,” said Kevin Wagner, a political science professor at Florida Atlantic University. “Part of that is [Democratic challenger] Patrick Murphy isn’t well-known in a lot of the state. Rubio is very visible.”

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Wagner said Rubio outperforms other Republicans among Hispanic voters, a key Democratic constituency. And Murphy, a U.S. representative from south Florida, faces a Republican-tilting electorate. Despite Florida’s reputation as a toss-up state, Democrats have struggled to win statewide office in recent elections.

“It’s fair to question some of the choices [Murphy’s] campaign has made,” Wagner said. “But I also think people’s expectations of taking on an incumbent senator were misplaced. It was always going to be difficult.”

Trump Looms Large in Pa. Senate Race
Pennsylvania features similar dynamics except that it has a much more Democratic-leaning electorate. Democrat Hillary Clinton currently enjoys a 7.5-point lead over Trump in the latest RealClearPolitics polling average.

Terry Madonna, director of the Franklin & Marshall College Poll, said Toomey needs Clinton voters to cross over and cast ballots for him. Such split-ticket voting has been declining over the past couple of decades, he said.

“I don’t think there’s any doubt we’ll see an uptick from four years ago,” he said.

[lz_table title=”Sabato’s Crystal Ball: Senate 2016″ source=””]
|Likely Democrat
Illinois (Kirk)
Wisconsin (Johnson)
|Safe Republican
Ohio (Portman)
|Likely Republican
Arizona (McCain)
|Leans Republican
Missouri (Blunt)
|Toss-up
Nevada (Retiring Democrat)
Indiana (Retiring Republican)
New Hampshire (Ayotte)
North Carolina (Burr)
Pennsylvania (Toomey)
[/lz_table]

But Madonna said it would be extremely difficult for Toomey to survive if Clinton pulls off a landslide in the Keystone State. He noted that Democrats four years ago, when President Obama won a 5-point victory in Pennsylvania, won every statewide race.

“This was the first time they had done that since the 1970s. That was that straight-ticket voting,” he said.

Democrats like their chances in Indiana, where former Sen. Evan Bayh has been leading in the polls to replace retiring Republican Dan Coates, although the former senator has been under fire concerning his residency.

North Carolina is another state where the presidential race could make a difference. Former Democratic state legislator Deborah Ross and incumbent Republican Richard Burr each have led three of the last seven polls and tied in the seventh. Likewise, the presidential race has see-sawed back and forth — although Clinton has had the upper hand in surveys released since the presidential debate.

If Clinton widens that lead, it could spell doom for Burr, who some Republican strategists grumble is a lackadaisical campaigner.

Pop-Up Mushroom Cloud in New Hampshire
That leaves New Hampshire, where Republican Sen. Kelly Ayotte and Democratic Gov. Maggie Hassan have been separated by more than 2 points in only one of a half-dozen public polls taken since August. Ayotte’s current RealClearPolitics lead is just 1.6 points.

“I think it’s going to go down to the wire … I’m still watching turnout,” said Andrew Smith, director of the University of New Hampshire Survey Center. “That’s the most important factor in determining who will win.”

[lz_table title=”Rothenbert & Gonzales Political Report: Senate 2016″ source=””]
|Pure Toss-up
Nevada (Retiring Democrat)
New Hampshire (Ayotte)
Pennsylvania (Toomey)
|Tilt Democrat
Indiana (Retiring Republican)
|Lean Democrat
Illinois (Kirk)
Wisconsin (Johnson)
|Tilt Republican
North Carolina (Burr)
Missouri (Blunt)
|Republican-favored
Arizona (McCain)
Ohio (Portman)
[/lz_table]

The tightness of the New Hampshire contest has produced some of the nation’s most out-of-the-box campaign tactics.

A provocative mailer features a pop-up of a mushroom cloud with information that Hassan supports Obama’s nuclear deal with Iran. Smith said New Hampshire voters have been deluged with mailers from both campaigns and outside groups as strategists shift away from TV ads.

“Each one is more and more goofy,” he said. “The mushroom thing at least was interesting because it was a pop-up.”

nuclear-mail
A direct mail piece in New Hampshire hitting Democratic nominee Gov. Maggie Hassan for supporting the Iranian nuclear deal features a pop-up mushroom cloud.

Like some other Republicans, Ayotte has danced around her support for Trump, saying she will vote for him but not endorse him. Smith contrasted Ayotte’s efforts, which are based on Trump’s personality rather than policies, with Strickland’s woes in Ohio.

“It’s going to be more difficult for him to separate himself from Clinton because it’s not based on personality, it’s policy,” he said. “I think it’s harder for Democrats [in Republican-leaning states] than it is for Republicans [in Democratic-leaning states].”

[lz_related_box id=”211558″]

In New Hampshire, a somewhat desperate gambit for the youth vote has been on full display with the Ayotte campaign giving out free condoms to college students. Smith noted that Clinton and millennial favorite Bernie Sanders have made repeated visits to the Granite State in an effort to boost youth turnout.

“They’re not confident that the young people are going to come out,” he said.

If millennial participation in New Hampshire falls, it could mean the difference between Sen. Mitch McConnell (R-Ky.) being the majority or minority leader come next year.