Sen. Ben Sasse Benjamin (Ben) Eric SasseChamber of Commerce endorses McSally for reelection Ben Sasse is mistaken with idea for the election of senators in America Big Ten football to return in October MORE (R-Neb.) said Friday that special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE "put Moscow on notice" with his investigative team's indictment of Russian individuals and entities who allegedly tried to sway the 2016 U.S. presidential election.

“Mueller just put Moscow on notice. This ought to be a wakeup call to Washington: Putin’s shadow war is aimed at undermining Americans’ trust in our institutions. We know Russia is coming back in 2018 and 2020 – we have to take this threat seriously," Sasse said in a statement.

Mueller's team brought charges against three Russian entities and 13 Russian nationals, alleging Russians took on the identities of real U.S. citizens to interfere in the 2016 election, an assessment similar to that previously reached by the U.S. intelligence community.

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The special counsel's team said in the indictment the efforts were aimed at helping 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's campaign and harming his opponent Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE, and that Russian operatives allegedly communicated with "unwitting individuals" associated with the Trump campaign.

Sasse, a member of the Senate Armed Services Committee, said in May that Russian tampering in American democracy "keeps me up at night" in regards to upcoming elections in 2018 and 2020.

“We know what the Russians are trying to do. We know that the technology around info-ops is getting better and better," he told NPR at the time.

Top U.S. intelligence officials testified before the Senate this week that intelligence agencies are expecting continued influence efforts by Russia in the upcoming 2018 midterm elections.