Bill Maher asked Issa during an interview on his show "Real Time" about reports that members of President Trump's campaign had contact with Russian officials.
Maher presented the Republican representative with a hypothetical scenario -- if Russians had hacked the campaign of GOP presidential nominee Mitt Romney in 2012 and if there had also been contacts between the Obama administration and the Russians.
"You're going to let that slide?" Maher asked Issa.
"No," Issa said.
"So you're not going to let this slide?" Maher followed up, referring to Russia and the Trump campaign.
"No," Issa said again.
When Maher then pushed Issa on the need for an independent investigation, the California Republican agreed that a special prosecutor is necessary. The investigation shouldn't be overseen by U.S. Attorney General Jeff Sessions, who was appointed by the president and was active in Trump's campaign, Issa said.
"You cannot have somebody -- a friend of mine, Jeff Sessions -- who was on the campaign and who is an appointee," Issa said. "You're going to need to use the special prosecutor's statute and office."
"There may or may not be fault," Issa said.
But he said, "The American people are beginning to understand that Putin ... is a bad guy ... We need to investigate [the Russian leader's] activities and we need to do it because they are bad people."