Sen. Al FrankenAl FrankenDrug pricing order would cut regulations Dems push for more action on power grid cybersecurity Congress poised to prohibit airlines from forcibly removing customers MORE (D-Minn.) said in an interview broadcast Sunday that he is "sure" there will be challengers to Hillary ClintonHillary Rodham ClintonReport: Biden scolded hedge fund manager over late son Poll: Former AG Lynch should be investigated OPINION: Dear media, Americans don't care about Obama's legacy 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 SandersBernie SandersSanders: ‘Thousands will die’ under GOP health bill A tale of two drug bills — one proposed bill will worsen the drug prices crisis The Hill's 12:30 Report MORE (I-Vt.) and Elizabeth WarrenElizabeth WarrenWhat does the working class want? Better schedules. Live coverage: Senate GOP unveils its ObamaCare repeal bill Overnight Regulation: Labor groups fear rollback of Obama worker protection rule | Trump regs czar advances in Senate | New FCC enforcement chief 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 CruzTed CruzUS gas exports not the elixir to European energy security Trump tells Democrats they need ‘courage’ to fix ObamaCare Fifth GOP senator announces opposition to ObamaCare repeal bill 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.