If I were them and had to choose one or the other — and it is essentially one or the other, as the Susan Collins crowd is unlikely to call both — I’d choose Bolton.

But I can see the argument for Mulvaney.

In any case, Chris Murphy understands that Democrats don’t really have a choice here. Bolton is gettable. Mulvaney is not, at least not without the sort of court battle that the Collins crew just won’t countenance.

That doesn’t mean the party doesn’t also want to hear from former national security adviser John Bolton about the administration’s decision to withhold aid to Ukraine. But in some Democrats’ view, all roads run through the acting White House chief of staff, who still technically runs the Office of Management and Budget.

“Mulvaney is most important. All of the testimony seems clear that this entire thing’s run through Mulvaney and Mulvaney’s the one talking to Trump on a regular basis,” Sen. Chris Murphy (D-Conn.) told reporters on Thursday, even if he’s not optimistic he’ll ever hear from the conservative budget hawk.

“But Mulvaney’s going to claim executive privilege and it will be tied up in courts,” Murphy said.

Mulvaney would indeed claim executive privilege. In fact, that may be the only reason he hasn’t been fired from the chief of staff job already. The media reported weeks ago that he’s on his way out — but not until impeachment is over. As long as Mulvaney remains a presidential aide, Trump’s legal grounds to silence him via executive privilege are stronger. Doubtless if Bolton were still NSA Trump would be working hard to prevent his departure for the same reason.

Why would Dems want Mulvaney instead of Bolton? For starters, he’s the (acting) chief of staff, the right-hand man who’s in on much of what happens around the president. Bolton knows only what Trump has said to him personally. Mulvaney knows what Trump has said to him personally — and possibly some of what he’s said to Giuliani, and Sondland, and Rick Perry, and Pompeo, and various other players.

Mulvaney’s also the head of OMB, the agency responsible for delaying the outlay of military aid to Ukraine — illegally, according to the GAO. Doubtless Mulvaney said to Trump at some point, “Why do you want this funding blocked?” What the president said back would be … important.

And of course Mulvaney’s the guy who delivered this answer at a press conference in October:

Democrats would want to go at him from both ends of that. Trump *never* mentioned the Bidens at any point in discussions about Ukraine? That’s surprising given Sondland’s belief that Trump’s only interest in Ukraine was what the country could do for him personally, starting with announcing the Burisma probe. And Trump *did* mention his interest in investigating possible Ukrainian interference in the 2016 election? Mulvaney thinks that’s A-OK since election security is a proper concern of the president, but didn’t he find it odd that Trump was letting dizzy Rudy Giuliani take the lead on that instead of, say, Bill Barr’s Justice Department or Mike Pompeo’s State Department?

It’s passing strange that Mulvaney saw nothing wrong with an anti-corruption effort that involved (a) shadow diplomacy involving shady cronies like Rudy and Lev Parnas instead of official channels and (b) an illegal hold on funding that had been duly appropriated by Congress. It’s not like Ukraine was a hostile power that required a back-channel approach either; Zelensky’s government was eager to ingratiate itself to the White House to solidify an alliance against Russia. All Trump had to do was have Pompeo ask. If, that is, everything was on the up-and-up.

Mulvaney is a thread intertwined with lots of other threads. Pull that thread and the garment could unravel. But that assumes he’d be forthcoming under oath and I don’t know that he would be. He’d have a lot on the line: He’s just 52 and has already served as a congressman, head of OMB, and chief of staff. He comes from a state, South Carolina, that’s solid red. If he finishes his service for Trump with the president’s good favor, the sky’s the limit for him potentially. He could end up with an even more influential cabinet job in Trump’s second term and be well positioned to run for governor in 2026. Or, if Lindsey Graham or Tim Scott ends up leaving the Senate for whatever reason, he’d be well positioned to succeed them. But if he were to incriminate Trump in Senate testimony, his career in Republican politics would be finished. He’d be washed up in his early 50s, a time when ambitious pols are looking at higher office.

Think he’d do it? Would a guy who got elected to Congress running as an ardent deficit hawk and then all but repudiated those beliefs because it was convenient for Trump really give Democrats what they’re looking for, even if he had the goods on the president? C’mon.

If the name of the game here for Schumer and Pelosi is winning a PR battle, i.e. damaging Trump at the trial despite the certainty of acquittal, Bolton’s more likely to deliver for them. He’s 71 so his career in public office is almost certainly over. He had a falling out with Trump as NSA and thus is apt to feel less personal loyalty to him than Mulvaney (who’s also allegedly in disfavor with the president, it should be noted) does. He’s working on a book about his time in the White House and sales of that book will doubtless be much, much higher if he prefaces its release with damning impeachment testimony than if he has nothing critical to say under oath about the Ukraine matter. He’s a much surer bet to play ball with Dems than Mulvaney is. If they’re forced to choose between the two, Bolton’s the logical pick.

Here’s Josh Hawley with his own thoughts about witnesses today. Hunter Biden’s testimony is becoming more relevant day by day, he insists, thanks to the Democrats’ own presentation.