Minnesota Sen. Al Franken on Thursday hit Republicans for what he called "startlingly ugly" rhetoric coming from the Republican National Convention this week.

"This is the kind of negativity, ugliness that you have come to expect from Donald Trump who started this campaign saying that Mexican immigrants were rapists and drug dealers," Franken said.

Franken said he found Wednesday's speech by vice-presidential candidate, Mike Pence, the Indiana governor to be the only positive highlight of the night. Previous speeches have been full of "constant attacks and very little of course about Donald Trump," he said.

"One thing I will say about Pence's speech it was refreshing to see someone say something good about Trump who wasn't actually related to him or stood to inherit a lot of his money. That's it -- on the good stuff."

Franken joined Democratic National Committee Chairwoman Debbie Wasserman Schultz and fellow Senate colleague, Cory Booker of New Jersey, who is among the finalists being considered for Hillary Clinton's vice-presidential pick.

Franken spoke only briefly before being overshadowed Booker who delivered an extended, and at times, personal, critique of the rhetoric coming from the convention. Afterward, Booker took various questions over the prospect Booker would join Clinton on the presidential ticket.