Wasn’t the door standing open all along? And would anyone want to walk through it even if it was removed from its hinges and burnt in the fireplace? The threat to call Hunter Biden or even Joe Biden serves mainly as a Republican bargaining chip to argue against expanding the House impeachment case by calling John Bolton and Mick Mulvaney, two witnesses that Adam Schiff and Jerrold Nadler declined to pursue in court through subpoenas but now demand that the Senate call at trial. Democrats from Chuck Schumer and Joe Biden himself on down insist that testimony from any of the Bidens would be “irrelevant” to the impeachment.

But would it? Former federal prosecutor Andrew McCarthy not only thinks that subpoenas to the Bidens have always been germane to the investigation, but that Schiff himself opened the door to relevance in his presentment of the articles:

Schiff’s point is that any presidential collusion with a foreign power that could influence the outcome of an American election is an abuse of power, period. …

It is fair enough to tut-tut that a president should not conflate foreign policy and domestic politics (something all of them do to some degree). And it would certainly be prudent (even if not constitutionally required) for presidents to leave questions about who should be investigated to the Justice Department, especially when a president’s political fortunes may be implicated. All that said, though, it makes a difference whether this president is asking the foreign power to manufacture a case against a political opponent, or whether the president is instead asking for an investigation into something that truly appears suspicious.

Schiff has ignored that salient distinction from the start. And by ignoring the difference, he has — however heedlessly — painted a bull’s-eye on the Bidens. The father and son were front and center within the first ten minutes of Schiff’s opening statement at the impeachment trial Wednesday afternoon. But that was old news. Schiff kicked the door open at the start of the very first House hearing. Not content to quote from President Trump’s actual call with President Zelensky of Ukraine, Schiff insisted on presenting a “parody” that, he maintained, conveyed the unspoken essence of Trump’s message: “I want you make up dirt on my political opponent, understand? Lots of it.”

In sum, the House’s chief prosecutor represented to the American people that President Trump had asked his Ukrainian counterpart to fabricate a false case against Biden. In any court in America, that would open the door to the Trump defense team to show that this was not the president’s intention at all; he was simply asking Zelensky to look into a situation that cried out for an inquiry.

In light of Schiff’s explicit allegation, the president is entitled to an opportunity to show that there was reason for him to believe that a notoriously corrupt Ukrainian energy company had retained Hunter Biden and paid him a fortune despite his lack of qualifications; and that later, despite the blatant conflict of interest, then–vice president Biden extorted Ukraine into firing a prosecutor who was investigating the company, threatening to withhold $1 billion in desperately needed funds.

This is almost an obvious point. If in fact there was a reasonable suspicion that Hunter Biden was part of a corrupt scheme, then Trump’s request for cooperation from Volodymyr Zelensky would not be problematic, even if it would still be pretty awkward. That means one positive defense to this is to pursue the theory that Biden’s hiring by Burisma and Joe Biden’s later intervention was part of their own quid pro quo. We already have Biden on video bragging about a quid pro quo, in fact, which Schiff made a part of his presentment by insisting that it had nothing to do with personal benefit to the Bidens.

That’s what McCarthy argues is an opening of the door to the defense to insist on subpoenaing the Bidens père et fils. Technically, McCarthy’s correct. Politically, though, it’s too much of a gamble in a trial that will inevitably acquit Trump anyway. The idea has the same defects as the House impeachment case — it’s totally speculative and suffers from a distinct lack of direct evidence. By now, Team Trump should have been able to dig up that evidence if it exists, especially with Rudy Giuliani’s activities in Ukraine. And if they did dig it up, they would have leaked it by now, even if that meant prematurely derailing Joe Biden’s presidential bid. If Republicans put the Bidens on the stand and get nothing out of them, it will seriously damage Trump’s overall political argument and end up bolstering Joe Biden’s standing.

As a counter-threat to a Bolton subpoena, it’s still relatively potent, though. Joe Biden’s mouth frequently operates without his brain in gear, which could lead to seriously problematic clips coming out of the trial that may or may not have much to do with the questions at hand here. No political party would allow its presumptive presidential nominee to be forced into testifying under oath in a political free-for-all. That makes all of this a tantalizing academic exercise, but not much more.