Despite Donald Trump's slide in the polls, a series of surveys released this week showed that some Republican Senate candidates are currently faring much better than the GOP nominee in their own states, raising the possibility that voters might be viewing the broader Republican Party separately from the real estate mogul. That dynamic could help boost Republicans hopes of keeping control of Congress, even if Trump loses at the top of the ticket.

GOP Senate candidates are ahead in Florida, Georgia, Iowa, and Ohio, all states where Trump trailed Hillary Clinton in the same surveys.

An NBC News/Wall Street Journal/Marist poll put Ohio Sen. Rob Portman ahead of his Democratic opponent, former Ohio Gov. Ted Strickland, 48 to 43 percent, even as Trump trailed Clinton 38 percent to 43 percent in the Buckeye State. Veteran Sen. Chuck Grassley has the support of 52 percent of Iowans, compared to Trump’s 37 percent.

In North Carolina, incumbent Republican Sen. Richard Burr trails Democrat Deborah Ross by 2 percent, compared to Trump's 9 percent deficit. In Pennsylvania, incumbent GOP Sen. Pat Toomey is behind Democrat Katie McGinty by 4 percent, while Trump is down by 11.

NBC News

The polls show that down-ballot GOP candidates have more support than Trump among self-described moderate voters in particular. In Ohio, Portman is effectively tied with Strickland among moderates, (Strickland is at 46, Portman 44), while Trump trails Clinton by 24 points among that same bloc.

Related: Clinton Running the Table in Key Battlegrounds

In Iowa, moderates favor Grassley over his Democratic opponent, while Trump trails Clinton by 18 percent among that bloc. In Pennsylvania, Trump was behind by 19 percent among moderates, while Toomey trailed by 4 percent.

Portman and Grassley are also getting more than 90 percent of the vote among self-described Republicans, a higher percentage of support than Trump receives from his own party.

Limiting The Damage

For now, the polls and expert projections suggest that Republicans could limit their overall losses in Congress, even with a sizable Clinton victory. According to the non-partisan Cook Political Report, Democrats are favorites to win 5 GOP-held seats in the House, while another 16 races are considered “toss-ups.” Even if Democrats won all 21 of those races, which is very unlikely, they would fall short of the 30 that the party needs to control the House. The GOP currently holds 247 of the House’s 435 seats.

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Related: Clinton's Lead Over Trump Increases in Three Battleground States

"Voters are not automatically punishing Republican candidates for Donald Trump's sins," said Nathan Gonzales, editor and publisher of the Rothenberg & Gonzales Political Report, a non-partisan newsletter that tracks congressional, gubernatorial and presidential campaigns.

He added, "In spite of Democratic attempts to couple every Republican to Trump, I think Trump is such a unique figure-- who had an established brand outside of politics before the race--that most voters don't think of him as a Republican or the leader of the party. But Democrats will prosecute that case over the next two months."

In the Senate, Democrats are favored in Illinois, Indiana, New Hampshire, Pennsylvania and Wisconsin. And Trump’s unpopularity in New Hampshire and Pennsylvania does appear to be dragging down GOP incumbents in those states in particular. Winning all 5 of these races would give the Democrats 51 seats and a majority.

But such a narrow majority would make it very difficult for the Democrats to run the Senate, requiring the party to be almost totally unified on every vote. And with just 51 seats, Democrats would face the prospect of losing the Senate in just two years, since the electorate in mid-terms tends to be older and whiter, Trump won’t be on the ballot in 2018 and Democrats are defending seats then in conservative-leaning states like Indiana and North Dakota.

The eight seats Democrats gained in 2008, amid Barack Obama’s landslide victory, helped the party keep Senate control from 2009 to 2014. This cycle is a major opportunity for Democrats to make up for the party's down-ballot losses in 2010 and 2014, win a significant majority in the Senate and make enough gains in the House to potentially win the chamber outright in 2020.

"I will do everything I can to help elect a Democratic Senate," Clinton said last week.

If the congressional elections continue on this course, the gridlock that defined the Obama years is likely to continue. A Republican House would block much of Hillary Clinton’s agenda, such as creating debt-free college education for most middle-class Americans. A Democratic Senate would similarly limit Trump’s policy goals if he were elected.

GOP Candidates Are Taking Aggressive Steps to Separate Themselves from Trump

Many Republicans, particularly the Senate candidates, are well-known figures with political brands that are distinct from Trump. So it is not surprising voters are not linking them with the real estate mogul.

Grassley has served as one of Iowa’s senators since 1981. Florida Sen. Marco Rubio ran for president against Trump, blasted the real estate mogul often and is unlikely to be associated with Trump’s controversial comments about Latinos, since Rubio himself is Cuban-American.

But these candidates are also following the guidance of party strategists, who even last fall were discussing how down-ballot Republicans could distance themselves from Trump. Ward Baker, who runs the Senate Republicans’ reelection arm, has urged GOP candidates to focus on local issues, as if they are running for sheriff. So Ohio’s Portman is campaigning on his work getting a bill through Congress to combat opioid abuse. He courted and then won the endorsements of several labor unions in the state, appealing to a traditionally-Democratic constituency.

Toomey of Pennsylvania is emphasizing his close ties with the state's police.

Speaker Paul Ryan developed a policy platform for House Republicans that did not include Trump’s most controversial ideas: deporting undocumented immigrants, building a large wall on the U.S.-Mexico border and banning Muslims from entering the country. Most Republicans in key races are following the Ryan model, and not campaigning on Trump's proposals.

“Distinguishing between the Trump brand and the Republican brand is the best way to maintain that down-ballot advantage for Republican incumbents,” said Whit Ayres, a Republican pollster who is working for the super-PAC of Rubio, who is ahead of his likely Democratic opponent, congressman Patrick Murphy, by 6 percent.

Democratic Candidates Are Going National

The Democratic playbook across the country in key races is to bash Trump and to link GOP House and Senate candidates to the real estate mogul. In a Northern Virginia district, Democratic House candidate LuAnn Bennett, running against a GOP incumbent, frequently visits mosques in the area as part of her campaign.

When Trump criticized the Khans, Bennett immediately praised the family, said Trump is “hostile to our Muslim community” and called for her GOP opponent, Barbara Comstock, to “withdraw” her support from Trump. (Comstock also praised the Khans. She has not endorsed Trump, but also has not joined the Republicans who say they will not vote for the real estate mogul.)

Catherine Cortez Masto, the Democrat running for the U.S. Senate seat in Nevada, said recently, “it is next to impossible to find” a difference on immigration policy between Trump and her Republican opponent, Joe Heck. That comment was so overstated that the website PolitiFact declared it “false.”

Unlike Republicans, Democratic candidates are aligning themselves with Clinton and the national party. Ohio’s Strickland and North Carolina’s Ross appeared with the former secretary of state when she came to their states recently, while McGinty of Pennsylvania went to the Democratic National Convention and praised Clinton in a speech.

These tactics may lead to Democratic victories in November, even if these candidates are trailing now. For Democrats, turning every down-ballot race into a proxy for Clinton v. Trump is perhaps the easiest path to victories.

Also, the best hope for Democrats overall is that 2016 is a “wave” election, in which national dynamics are more important than local ones. In 2008, the unpopularity of George W. Bush, the Wall Street collapse and the excitement around Obama resulted in nearly every close race tipping to Democrats.

The inverse happened in 2014. With an electorate frustrated with Obama, Democrats lost U.S. Senate races in states where the party is generally strong (Iowa, Colorado) and were blown out in elections that were expected to be close (Kentucky.)

If Clinton continues to lead Trump by more than 6 percent, as she has in polls released after the Democratic National Convention, that could sweep other Democrats into office. A recent poll in New Hampshire showed incumbent Republican Sen. Kelly Ayotte trailing her Democratic opponent by 10 percent, even as the survey illustrated that a plurality of voters in the state view Ayotte favorably.

If Trump trails Clinton by 15 percent in New Hampshire, as that poll suggested, Ayotte has very little chance of winning reelection.

A true wave could make it difficult even for deeply-entrenched incumbents. Polls suggest that Arizona's John McCain, who has held his seat since 1987, is in danger of losing, particularly if there is a strong anti-Trump turnout among the state's Latinos.

“If Trump wins in states like Florida, New Hampshire, Ohio or Pennsylvania, there’s every reason to think those Republican incumbents will also win,” said Kyle Kondik, an elections expert at the University of Virginia’s Center for Politics.

“But if he doesn’t,” Kondik added, “the Republican senators will have to run ahead of Trump. They may be able to do so by several points, but that’s where Trump’s margin matters. If Clinton runs at or ahead of Obama in any of these states, I would think it would get much harder for these incumbents to hang on.”

"It's unwise to rule out a Democratic majority in the House," said Gonzales. "If a wave develops against the Republicans, House races could be one of the last places where it is felt. In some past wave elections, such as 2006, we didn't see the wave until September."