Story highlights Bernie Sanders won the Democratic primaries in Wisconsin and Michigan

Donald Trump's campaign manager said Sanders softened Hillary Clinton's base

(CNN) Donald Trump's campaign manager Kellyanne Conway said she believes the race would have been tougher for the President-elect had Hillary Clinton chosen Bernie Sanders as her running mate.

CNN's Jake Tapper asked Conway on "State of the Union" if she thought the Vermont independent and primary challenger to Hillary Clinton would have made her job tougher had he been added to the Democratic ticket.

"Yes," she told Tapper during a special edition of CNN's "State of the Union," filmed at Harvard University's Institute of Politics in Cambridge, Massachusetts. "And Bernie Sanders -- I'd also like to publicly thank Bernie Sanders for his effect on our campaign because he softened up Hillary Clinton. He won 22 states and 13 million voters, and that ain't nothing."

Sanders beat Clinton in the Democratic primaries in Michigan and Wisconsin -- states that Trump won in the general election.

But Conway said those Sanders supporters didn't fully come around for the former secretary of state even after Sanders endorsed her and she won the nomination at the Democratic National Convention.

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