CBS News reporter Ed O’Keefe asked Joe Biden about his feud with Sen. Bernie Sanders and a tense exchange followed with the vice president asking “why, why, why” and telling O’Keefe to “calm down.”

Gayle King: Vice President Biden may want to avoid the impeachment trial but he’s not backing away from his feud with Bernie Sanders. Ed O’Keefe caught up with him in Des Moines, and they had, how do we describe this, Ed? This “remarkable” exchange is the word?

Ed O’Keefe: That’s one way of putting it, Gayle. We wanted to ask the Vice President why he’s feuding again with Bernie Sanders. Remember, earlier this week he told us he accepted Sanders’ apology after one of his supporters called the former vice president “corrupt.” But, within hours, both camps were out with dueling attack videos.

Biden calling out “Bernie’s negative attacks” and Sanders raising questions about Biden’s previous willingness to fiddle with federal benefits. While Sanders is in Washington dealing with impeachment, Biden was out here talking to voters. So, we wanted to ask him, why this change in strategy? Take a look.

O’Keefe (yelling question at Biden): Yesterday you said you accepted Bernie’s apology, now you’re attacking him. Why are you doing that? Why wasn’t his apology enough, Mr. Vice President? Why attack Sanders?

Joe Biden: Why, why, why, why, why, why… you’re getting nervous, man. Calm down, it’s OK. He apologized for saying that I was corrupt. He didn’t say anything about whether or not I was telling the truth about Social Security.

King: Ed, I wasn’t sure where that was going, what were you thinking?

O’Keefe: Look, we ask the candidates questions, how they respond is up to them. Clearly, in this case, Biden, a little touchy. He’s sensitive to this charge that he wants to change up Social Security. Yes, as a Senator in the 1990s he was open to making changes to federal benefits to balance the budget, but now as a presidential candidate, he says he wants to preserve and expand Social Security in part because seniors are living longer.

How exactly we would pay for it is a detail to be sorted out later. But, look, with Biden and Sanders either tied or first and second here in Iowa and across the country, this is a feud that is likely to continue with eleven days until the Iowa caucus.

King: First it seemed like he didn’t want to answer, but he turned around so I give him credit for that.

MORE VIDEOS

Full Video: Day 6 of President Trump Impeachment Trial in U.S. Senate

Day six of the trial on Monday, Jan. 27, 2020. Alternate Video Links: Fox News (YouTube), NBC News (YouTube) Watch prior days: Day 2 (Jan 22) ...

Bernie Sanders Responds to Hillary Clinton Saying “Nobody Likes Him”

Sen. Bernie Sanders of Vermont was questioned about a new documentary in which former secretary of state Hillary Clinton says "nobody likes" Bernie in...

Full Video: NBC/MSNBC Democratic Debate From Las Vegas, Nevada (Feb 19)

Six Democratic candidates, including former New York City Mayor Michael Bloomberg, took the stage at the Paris Theater in Las Vegas for a debate...

Highlights From Week 1 of President Trump Senate Impeachment Trial

Highlights from the first week of President Trump's impeachment trial in the U.S. Senate. Scroll down for highlights from each day from week 1...

Full Video: Day 4 of President Trump Impeachment Trial in U.S. Senate

Full video of day four of the trial on Friday, Jan. 24, 2020. The impeachment trial of President Donald Trump began on Tuesday, Jan. 21,...

Hillary Clinton Says “Nobody Likes” Bernie Sanders in New Documentary

Report from CBS News on a new documentary in which former secretary of state Hillary Clinton says that nobody in Congress likes Sen. Bernie...