Republican strategist Alex Castellanos on Sunday said the Democratic Party has flourished under 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 presidency, pointing to the party's sweeping election wins on Tuesday.

“Donald Trump has made the Democratic Party great again,” Castellanos said on ABC's "This Week."

“He’s unified it and given it intensity at the polls much like President Barack Obama Barack Hussein ObamaMomentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina Majority of voters say Trump should not nominate a Supreme Court justice: poll MORE unified and intensified the Republican party,” he said during a roundtable discussion.

Castellanos predicted that Trump being in office will continue to negatively impact the Republican Party's efforts to protect and win seats in the upcoming 2018 midterm elections.

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“If you look ahead at 2018 — those Republican districts that 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 won, 23 of them — the House is in play,” Castellanos said.

His remarks come after Democrats won elections from coast to coast on Tuesday, including the two gubernatorial races in Virginia and New Jersey.