DES MOINES, Iowa — Former Vice President Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE responded to Iowa Sen. Joni Ernst Joni Kay ErnstSenators offer disaster tax relief bill Conservatives see glaring omission on Trump's Supreme Court shortlist Senate Republicans scramble to contain fallout from Woodward bombshell MORE (R) on Sunday after she suggested he could be impeached if he wins the presidential election.



“Why don’t you all show Joni Ernst just how smart you are by caucusing for me?” Biden joked to a room full of supporters, to loud applause.



“I promise if you stand with me, we will end Trump’s reign of hatred and division,” Biden said.



Biden was occasionally interrupted by protesters urging him to shun contributions from fossil fuel companies. The former vice president was speaking to a crowd of more than 1,000 supporters at a middle school in Des Moines, Iowa, one of the largest crowds his campaign has attracted to date.

His remarks came in response to comments Ernst made in an interview with Bloomberg, where she suggested that Biden could be impeached if elected for supposedly "turning a blind eye to Burisma because his son was on the board making over a million dollars a year.”

“I think this door of impeachable whatever has been opened,” Ernst told the news outlet. “Joe Biden should be very careful what he’s asking for because, you know, we can have a situation where if it should ever be President Biden, that immediately, people, right the day after he would be elected would be saying, ‘Well, we’re going to impeach him.’”

The senator previously suggested that the impeachment trial could be used to hurt Biden's chances in the Iowa caucuses on Monday.

John Bowden contributed to this report.