"He should be impeached for so many things," state Sen. Glenn Grothman (R) said at the forum.
"You begin to see the markings of a totalitarian state," he added about the pattern created by the administration's IRS and NSA scandals.
State Sen. Joe Leibham (R) said that if Obama lied about how much he knew about the IRS scandal, that would be "grounds for impeachment."
"His presidency is a scandal," Leibham said. "He has destroyed America from the great capitalistic country it used to be."
State Rep. Duey Stroebel (R) said the administration's response to the Benghazi attack topped his list of scandals.
"President Obama is doing his best to tear the country down," Stroebel added later.
Tom Denow, the fourth candidate who has never held elected office, agreed with the other candidates that a special prosecutor should investigate the IRS scandal, according to the Journal Sentinel.
Whichever candidate wins the conservative district's August primary will face Democratic Winnebago County Executive Mark Harris in the general election. On Friday, he dismissed the four GOP candidates' talk of impeachment.
"I suspect that's just throwing something to the most extreme elements of their party," he told the Journal Sentinel.
[H/t Andrew Kaczynski]