After that Friday interview, Biden critics were quick to point out that the second article of impeachment against Trump concerned his defiance of congressional subpoenas — albeit on a broad and indiscriminate basis — but Biden says there’s no comparison between him and Trump.

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. — Joe Biden (@JoeBiden) December 28, 2019

“I want to clarify something I said yesterday,” Biden tweeted on Saturday. “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.”

“But,” he continued, “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.”

One of Biden’s Democratic rivals, Sen. Elizabeth Warren, agreed that Trump was trying to shift the focus from the president’s “abuse of power.” But she told reporters Saturday that she assumed Biden would honor a congressional subpoena.

"He has said he always follows lawfully-issued orders, and if there is a lawfully-issued order for a subpoena, then he should follow it,” she said.

For Biden, the controversy is as much political as it is personal.

Trump’s impeachment revolves around the president’s attempt to get Ukraine to investigate Biden over his son’s business dealings in the country when the former vice president was involved in withholding aid to the country to clean up corruption. The controversy led to a fiery clash between Biden and an Iowa farmer earlier this month, but some voters were still left with questions about son Hunter Biden’s business deals.

While Trump has tried to draw a link between the Bidens and Ukraine, no illegal activity has been found. And Trump administration witnesses during his impeachment inquiry testified that Biden did nothing illegal in Ukraine. Some, however, said Hunter Biden’s business deal raised the specter of a possible conflict of interest.

Biden reiterated Saturday that he and his son are not germane to the case against Trump leveraging aid to Ukraine in return for an investigation of a political rival.

“The subpoenas should go to witnesses with testimony to offer to Trump’s shaking down the Ukraine government — they should go to the White House,” Biden wrote.

Earlier this month, when asked about the appearance of a potential conflict of interest, Biden told reporters in Iowa that his son “spoke publicly about it. He said that in retrospect if he had thought about what was going to happen — how it was going to be handled by Giuliani and company — he wouldn’t have done it. Nothing he did [was] wrong. The appearance looked bad. And he acknowledged it. And that’s it. That’s all I’m going to talk about.”

But when asked if he shared his son’s view about how “the appearance looked bad,” Biden wouldn’t say.

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On Friday, Biden was asked by the Des Moines Register if he would defy a subpoena, leading him to indicate he would.

“Correct,” he responded. “And the reason I wouldn't is because it's all designed to deal with Trump doing what he's done his whole life, trying to take the focus off him.”

Biden also rejected the notion that defying a subpoena would put him above the law, noting that "the grounds for them to call me would be overwhelmingly specious, but so, I don't anticipate that happening anyway. But what it would do if I went — let's say I voluntarily just said, let me go make my case.”

Biden also repeated his statement that him testifying would be a distraction.

“What are you going to cover?” Biden asked the paper. “You guys are going to cover for three weeks anything I said. And he's going to get away. You guys buy into it all the time … Think what it’s about. It's all about what he does all the time, his entire career. Take the focus off. This guy violated the Constitution. He said it in the driveway of the White House. He acknowledged he asked for help.”