 -- Sen. Bernie Sanders called the Republican Party "a joke" during an interview Wednesday evening and he didn’t stop there.

Sanders said the GOP race is a "national disgrace" and an "international embarrassment."

"What Republican candidates have now stooped to is to starting attacking each other's wives," the Vermont senator and presidential hopeful told MSNBC’s Rachel Maddow. "I mean this is an international embarrassment. I think people around the rest of the world think we are pretty crazy."

The underdog candidate vying for the Democratic Party nomination said that comparatively he and his opponent, former Secretary of State Hillary Clinton, have been playing nice and focused on the issues. Citing several issues ranging from income inequality to climate change, he argued that he believes the GOP is out of touch with voters and has become a "fringe party."

Earlier in the day, the Vermont senator told a packed house in Madison, Wisconsin, that the American people were "flabbergasted" by this year’s Republican race and the low blows from the candidates on the other side were "beyond comprehension to average Americans." He specifically chastised Donald Trump for his recent comments on abortion.

Ahead of next week’s primary in the state, Sanders spent the last two days crisscrossing Wisconsin and took the opportunity to criticize one Republican in particular: the state’s governor, Scott Walker. Sanders blasted Walker on issues ranging from wages and unions to voting rights at each of his rallies.