Biden reacts to coming impeachment vote, tight race with Bernie Sanders

In an exclusive interview on ABC News' "Good Morning America," former Vice President Joe Biden gave his reaction to the ongoing impeachment trial of President Donald Trump in the U.S. Senate and the latest comments from two of his top rivals for the Democratic nomination, Sen. Bernie Sanders and former South Bend, Indiana, Mayor Pete Buttigieg.

On impeachment, Biden expressed exasperation at the defense from Trump's team.

"I find this defense astounding. 'Yeah, he did it, but it doesn't matter.' I mean, George Washington is rolling over in his grave," Biden told ABC News Chief Anchor George Stephanopolous.

When pressed by Stephanopolous over comments he made during the 1999 impeachment trial of President Bill Clinton warning against impeachment votes along party lines, Biden pushed back, saying the facts make it clear that Trump has violated the Constitution.

"It's not a partisan impeachment. He violated the constitution, period," Biden said. "Even if it's party line vote, it just ... reflects on those who know, in fact, in their heart and their head that, in fact, it's a violation of the Constitution to do what he did."

With the Iowa caucuses only three days away, Biden acknowledged he is neck and neck in recent polling with Vermont Sen. Sanders, seeming to manage expectations with the unpredictable race.

"If there is a big snowstorm in certain parts of the country, certain parts of the state it could have an effect. So the caucus is, you have to be able to come to a gymnasium, stay there for two, three hours, and it takes a lot of commitment. We will see would shows up," Biden said.

Despite the uncertainty, Biden said he's "feeling good" about the race in Iowa and his chances in other states as well.

Biden was also asked about comments he made Thursday about Sanders implying that the senator from Vermont, who pledged to run for president as a Democrat, is not a member of the party.

"Look, Bernie is a Democrat. Bernie is -- he calls himself a Democratic socialist -- we have a different view on a lot of things. He's a decent guy. That wasn't the question. The question is, whether or not who is best prepared on day one to try to reunite this party and the country as well as stand on the world stage and reassert our role in the world," Biden said.

Biden said that he will support the Democratic nominee, regardless of who wins the nomination.

The former vice president additionally weighed in on fellow moderate Democratic candidate Buttigieg and his decision to go after Biden for using a "Washington playbook" that he says won’t work against Donald Trump.

"The reason I’m running because of my experience, George. With experience comes a little bit of judgment and wisdom, and I have a record of pulling things together," Biden argued.

"I'm running because of the fact I have this experience, not in spite of the fact that I have this experience," he added.

The former vice president has been aggressively campaigning in Iowa in the final days until the caucuses, embarking on a nine-day bus tour that is crisscrossing the state as he makes his final pitch to the voters.

In the waning days of the campaign in Iowa, Biden has leaned heavy into the message that he is the candidate that can best unify the Democratic party and withstand a bruising general election campaign with Trump.

In a speech billed as a pre-buttal to Trump's rally in Des Moines on Thursday morning, Biden argued that the "character of the nation," is on the ballot in the 2020 election.

"Does it matter if a president lies? Does it matter if a president has no moral compass? Does it matter if a president believes they're above the law? Does it matter if a president is petty? Mean? Cruel? Spiteful? Does the character of a president matter? I believe the answer to each and every one of those questions is 'Yes,'" Biden told a crowd in Waukee, Iowa, on Thursday.

Biden continues his final push to Monday's caucuses with three more campaign events in eastern Iowa on Friday.