IOWA CITY, Iowa — Former Vice President Joe Biden said during a campaign town hall he wanted "no part" of a deal between Democratic and Republican lawmakers.

“The reason I would not make the deal, the bottom line is — this is a constitutional issue,” Biden said Wednesday afternoon in Osage, Iowa. After being asked whether he would offer testimony during the impeachment trial if it meant White House chief of staff Mick Mulvaney or former national security adviser John Bolton would also receive subpoenas, Biden replied, “We’re not going to turn it into a farce or political theater. I want no part of that.”

Biden then defended his son, Hunter Biden, who has been accused of improperly serving on the board of the Ukrainian energy company Burisma Holdings.

“No one has suggested my son did anything wrong,” Biden said. “There’s nobody that’s indicated there’s a single solitary thing he did that was inappropriate or wrong other than the appearance. It looked bad that he was there."

In December, Biden said he would ignore a Senate subpoena, a position he would take several times before walking it back. A number of House and Senate Republicans have long said testimony from both Hunter Biden and Joe Biden would damage the Democrats' case against the president.

"I want to clarify something I said yesterday. In my 40 years in public life, I have always complied with a lawful order and in my eight years as VP, my office — unlike Donald Trump and Mike Pence — cooperated with legitimate congressional oversight requests," Biden tweeted on Dec. 28. "But I am just not going to pretend that there is any legal basis for Republican subpoenas for my testimony in the impeachment trial. That is the point I was making yesterday and I reiterate: this impeachment is about Trump’s conduct, not mine."

Last week, Sen. Ted Cruz proposed a "witness reciprocity" plan to party leadership that would trade a subpoena for Biden with subpoenas for Bolton and Mulvaney. At the time, Senate Majority Leader Mitch McConnell seemed open to the idea.

"We’ll be dealing with the witness issue at the appropriate time into the trial, and I think it’s certainly appropriate to point out that both sides would want to call witnesses if they wanted to hear from them,” he said.

Several Senate Democrats have privately mulled that they are considering such a trade, saying Bolton's and Mulvaney's testimonies are crucial to making their case against Trump.