Bernie Sanders. REUTER/Carlos Barria The campaign arm of House Republicans used Soviet imagery in a Bernie Sanders-themed fundraising pitch.

The National Republican Congressional Committee released a fundraising note aimed at Sanders, the Democratic presidential candidate. With a large hammer and sickle image on the page, the pitch urged Republicans to "take a stand against socialism" by donating.

"It’s a real possibility that the Democrats may actually nominate a socialist," the fundraising letter said. "Self-proclaimed socialist Bernie Sanders is catching fire in the Democrat primary. He's smashing online fundraisng [sic] records and has even reported over two million online donations."

It continued: "We have to stop this! Pitch in today to keep America free from socialism."

The fundraising pitch comes as Sanders, a self-avowed democratic socialist, has attempted to quell concern among some Democrats. Those Democrats, many of whom support Democratic rival Hillary Clinton, have expressed fear that being on the same ticket as Sanders could alienate more moderate voters in swing states and districts.

Sanders has aggressively countered the impression that his nomination would not bode well for Democrats in a general election, pointing out that he performs well in theoretical head-to-head matchups with some Republican presidential candidates.

On Sunday, Sanders said the enthusiasm he's generated behind his insurgent candidacy will motivate irregular and first-time voters to participate, which he asserted will propel him and other Democrats to victory.

"I think in fact, Hillary Clinton will be the problem," Sanders told NBC's Chuck Todd on "Meet the Press."

"Because I think our campaign is the campaign that is generating excitement and energy that will result in a high voter turnout. Republicans win when voter turnout is low. Democrats win when voter turnout is high," he continued. "I think our campaign is raising issue about a rigged economy, a corrupt campaign-finance system."

Clinton on Sunday suggested she agreed with lawmakers like Sen. Claire McCaskill (D-Missouri), who has said that Republicans "can't wait to run an ad with a hammer and sickle" against Sanders.

"That certainly is what a lot of Democratic leaders are saying, and I take them at their word," Clinton said when asked about concerns about how Sanders would affect Democrats down the ballot.

"They know their states. They know the country. They know we have to take back the Senate," she continued. "They want to make some advances in the House as well as at governor and legislature levels across the country."

An image from the NRCC fundraising page. NRCC Republicans haven't been shy in expressing their enthusiasm about Sanders' rising popularity among Democratic voters.

During the last Democratic debate, the Republican National Committee sent out a series of emails fact-checking Clinton's attacks on Sanders. Last week, a super PAC founded by a prominent Republican donor also began running attack ads against Sanders in Iowa that actually touted traits that Democratic voters support.

Republican candidates themselves have begun to criticize Sanders' ideology.

During last week's Republican presidential debate, Sen. Marco Rubio (R-Florida) garnered one of the biggest applause lines of the night by knocking Sanders' identify as a Democratic-socialist.

"Bernie Sanders is a socialist. I think Bernie Sanders is a good candidate for president — of Sweden," Rubio said. "We don't want to be Sweden, we want to be the United States of America."