Sen. Al FrankenAlan (Al) Stuart FrankenVirginia can be better than this Harris off to best start among Dems in race, say strategists, donors Virginia scandals pit Democrats against themselves and their message MORE (D-Minn.) said in an interview broadcast Sunday that he is "sure" there will be challengers to Hillary ClintonHillary Diane Rodham ClintonFemale Dems see double standard in Klobuchar accusations Klobuchar, O'Rourke visit Wisconsin as 2020 race heats up McCabe's shocking claims prove the bloodless coup rolls on MORE in the Democratic presidential primary. 

Asked on CNN's "State of the Union" if Democrats need a spirited primary, Franken said of Clinton, "I very much doubt that she’ll be the only one. I’m sure someone will jump in."

"I don’t know how you make someone else viable, they have to make themselves viable, but I’m sure that there will be a number of other people in the race," Franken added. 

Clinton is by far the frontrunner for the Democratic nomination. Other names that have surfaced for a run are Sens. Bernie SandersBernard (Bernie) SandersSenate Dems introduce bill to prevent Trump from using disaster funds to build wall Klobuchar, O'Rourke visit Wisconsin as 2020 race heats up Sherrod Brown pushes for Medicare buy-in proposal in place of 'Medicare for all' MORE (I-Vt.) and Elizabeth WarrenElizabeth Ann WarrenSenate Dems introduce bill to prevent Trump from using disaster funds to build wall Klobuchar, O'Rourke visit Wisconsin as 2020 race heats up Sherrod Brown pushes for Medicare buy-in proposal in place of 'Medicare for all' MORE (D-Mass.), though Warren denies she will run. Maryland Gov. Martin O'Malley (D) is also a possibility. 

Franken reflected on the lesson of the midterms by saying Democrats need to fight for the middle class while also working across party lines. 

After his razor-thin 2008 victory, the former "Saturday Night Live" star said, "There were, I think, a lot of Minnesotans who didn’t quite know what to expect, but what they saw is I worked every day in what I saw as the interests of Minnesotans, and I worked across party lines to find common ground."

"While I found common ground, I stood my ground when the powerful would come after the middle class or those aspiring to be in the middle," Franken said. 

Franken, a leading proponent of net neutrality rules for the Internet, also hit back against Sen. Ted CruzRafael (Ted) Edward CruzEl Chapo's lawyer fires back at Cruz: 'Ludicrous' to suggest drug lord will pay for wall Democrats have a chance of beating Trump with Julian Castro on the 2020 ticket Poll shows competitive matchup if O’Rourke ran for Senate again MORE (R-Texas), who called net neutrality "ObamaCare for the Internet."

"He has it completely wrong and just doesn't understand what this issue is," Franken said.