Republicans are eagerly watching Sen. Bernie Sanders Bernie SandersNYT editorial board remembers Ginsburg: She 'will forever have two legacies' Two GOP governors urge Republicans to hold off on Supreme Court nominee Sanders knocks McConnell: He's going against Ginsburg's 'dying wishes' MORE’s (I-Vt.) surge toward the Democratic presidential nomination.

GOP lawmakers and strategists believe Sanders, who identifies as a democratic socialist, is not only beatable in November but could have a disastrous down-ballot impact for Democrats in key congressional races.

“I would think that in a lot of those swing states it’s a very complicated factor to have him at the top of the ticket if you’re a down-ballot Democrat running for House or Senate, I would be really concerned,” said Sen. John Thune John Randolph ThuneWhat Senate Republicans have said about election-year Supreme Court vacancies The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump contradicts CDC director on vaccine, masks MORE (S.D.), the No. 2 Senate Republican.

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Asked if he thought Sanders’s surge was a “blessing,” Sen. John Cornyn John CornynCalls grow for Biden to expand election map in final sprint Bipartisan praise pours in after Ginsburg's death Chamber of Commerce endorses McSally for reelection MORE (R-Texas), who is up for reelection, called it “a little scary that there would be that much support for an avowed socialist.”

“It splits the Democratic voters, the people who don’t like President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE very much but when presented with that option might say, ‘Well I’m not going to vote for a socialist. I’ll vote for President Trump rather than do that,’ ” Cornyn said.

The predictions that a Sanders nomination would be a headache for Democrats comes as he holds a lead in the hunt for delegates while moderates remain torn among several potential alternatives.

Sen. Marco Rubio Marco Antonio RubioSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Florida senators pushing to keep Daylight Savings Time during pandemic Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll MORE (R-Fla.), in a video taken while he appeared to be driving down a road, said “unless the Democratic establishment steals it from him,” Sanders would be the nominee.

“It’s a big deal for America, and I hope people start waking up to that reality,” Rubio added.

Sanders, who has diversified his base since his failed 2016 White House run, is showing up as a boogeyman for Republicans looking to defeat Democrats up and down the ballot.

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Steve Guest, the Republican National Committee’s rapid response director, argued on Monday that Sanders’s ideas are a “danger to America and to our way of life.”

“Good luck Democrats who may try and distance themselves from Sanders’s praise of communist dictators,” he added.

Sanders caused a headache for Florida Democrats on Monday when the National Republican Congressional Committee (NRCC) seized on remarks about Cuba he made the night before on “60 Minutes,” saying that “it’s unfair to simply say everything is bad” just because it is associated with Fidel Castro.

In two separate email blasts by the NRCC, the group questioned if Florida Reps. Donna Shalala Donna Edna ShalalaShakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' Hillicon Valley: Dems seek to expand DHS probe after whistleblower complaint | DHS rejects House subpoena for Wolf to testify | Facebook rolls out new features for college students Democrats call for narrowing digital divide to help students during pandemic MORE (D) and Stephanie Murphy Stephanie MurphyDemocrats scramble on COVID-19 relief amid division, Trump surprise Bank lobbying group launches ad backing Collins reelection bid House Democrats call on State Department for information on Uighur prisoner Ekpar Asat MORE (D) would support a “Castro fanboy.” Both have disavowed Sanders’s comments.

“Does this mean Stephanie Murphy will refuse to support Sanders when he is the nominee? Or will she upset her socialist base instead?” asked Camille Gallo, a spokeswoman for the NRCC.

A GOP strategist pledged that Republicans would use Sanders as an anchor to pull down Democratic Senate hopefuls.

“Right now, Bernie is their front-runner, and socialism doesn’t sell in the Atlanta suburbs, in their Charlotte suburbs and in the Phoenix suburbs,” the GOP strategist said, referring to the Senate races in Georgia, North Carolina and Arizona.

Sanders, who supports free college education and “Medicare for All,” is already being name-dropped in key Senate races as Republicans try to activate their base. While most of the 24 Senate seats the GOP is defending are in safe Republican states, a handful of key toss-up races are expected to make or break the GOP efforts to hold onto the majority.

Sen. Cory Gardner Cory Scott GardnerJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Gardner on court vacancy: Country needs to mourn Ginsburg 'before the politics begin' MORE (R-Colo.), appearing with Trump at a Colorado rally last week, pledged that Republicans would fight “socialism.”

“There was a dangerous thing that happened in 2016. It was the normalization of socialism by Bernie Sanders,” he said.

Sen. Martha McSally Martha Elizabeth McSallyTrump supporters chant 'Fill that seat' at North Carolina rally Momentum growing among Republicans for Supreme Court vote before Election Day Vulnerable GOP incumbents embrace filling Supreme Court seat this year MORE (R-Ariz.) recently called former astronaut Mark Kelly, who is likely to be her Democratic opponent, the “the 51st vote for all of Bernie’s wildest Soviet-style fantasies.”

McSally is running for the final two years of the late Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE’s (R) term. Kelly, the husband of former Rep. Gabrielle Giffords (D-Ariz.), has distanced himself from the tag, noting that he’s a “capitalist.”

Former Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE, who is trying to reclaim his old Senate seat in Alabama, sent out a fundraising blast earlier this month after Sanders won New Hampshire, warning about the spread of “socialism.”

“I know Bernie Sanders well. I confronted his extreme ideas and spending policies for years on the Senate Budget committee where we both served. I went toe to toe many times with him. I was the leading opponent of these extreme ideas on the committee,” he said in the email to supporters.

Republicans have worked for months to make the 2020 election a referendum on “socialism.” It’s a narrative they think is a good fit for Sanders.

An ABC News-Washington Post poll found that 31 percent of adults say they would be less likely to support Sanders if he was labeled as a democratic socialist and 38 percent said so when labeled as a socialist.

Even as Republicans have worked overtime to make Sanders the face of the Democratic Party, there are a slew of warning signs against underestimating the 78-year-old’s potential strength as a general election candidate.

An ABC News-Washington Post poll found Sanders leading Trump in a potential head-to-head match-up, similar to several of the Democratic candidates.

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It also found that 30 percent of Democrats or Democratic-leaning voters believe Sanders is the best choice to beat Trump — the highest percentage for anyone in the still-crowded 2020 primary field.

Sen. Tim Scott Timothy (Tim) Eugene ScottAuthor Ryan Girdusky: RNC worked best when highlighting 'regular people' as opposed to 'standard Republicans' Now is the time to renew our focus on students and their futures GOP lobbyists pleasantly surprised by Republican convention MORE (R-S.C.) warned during an interview with “CBS This Morning” that he thought Sanders is Trump’s most difficult potential opponent.

“I would say that the biggest threat to President Trump is President Trump. ... If there is a second choice other than himself it would be Bernie Sanders. Bernie Sanders brings that outside game in a similar fashion that President Trump did in 2016,” Scott said Monday.