Sen. Al FrankenAlan (Al) Stuart Franken#BelieveAllWomen, in the Ellison era, looks more like #BelieveTheConvenientWomen The Hill's Morning Report — GOP seeks to hold Trump’s gains in Midwest states Dems make history in Tuesday's primaries MORE (D-Minn.) said Sunday that Donald TrumpDonald John TrumpWhite House counsel called Trump 'King Kong' behind his back: report Trump stays out of Arizona's ugly and costly GOP fight Trump claims he instructed White House counsel to cooperate with Mueller MORE's final ad, which includes multiple Jewish Americans, is "something of a German Shepherd whistle."

"Well, when I saw the ad, I thought that this was something of a German Shepherd whistle, a dog whistle, to sort of the certain group of the United States," Franken told CNN's Jake Tapper on "State of the Union."

"I think that it does speak to a certain part of his alt-right base. [Steve] Bannon, I mean, who's head of Breitbart, is his chairman. They traffic in that," said Franken.

In a closing pitch to American voters, the Republican presidential nominee's campaign released a two-minute ad showing Federal Reserve Chairwoman Janet Yellen, Goldman Sachs CEO Lloyd Blankfein and George Soros. All three are Jewish.

"Trump has retweeted a lot of that sort of thing. And I think that it's an appeal to some of the worst elements in our country as a closing argument," Franken added.