The scandal that's likely to lead to Donald Trump's impeachment involves a striking cast of characters. In addition to the president himself, there's a growing list of questions involving Secretary of State Mike Pompeo and Attorney General Bill Barr, among others, and those questions need answers.

President Trump repeatedly involved Vice President Pence in efforts to exert pressure on the leader of Ukraine at a time when the president was using other channels to solicit information that he hoped would be damaging to a Democratic rival, current and former U.S. officials said. Trump instructed Pence not to attend the inauguration of Ukrainian President Volodymyr Zelensky in May — an event White House officials had pushed to put on the vice president's calendar — when Ukraine's new leader was seeking recognition and support from Washington, the officials said. Months later, the president used Pence to tell Zelensky that U.S. aid was still being withheld while demanding more aggressive action on corruption, officials said. At that time — following Trump's July 25 phone call with Zelenksy — the Ukrainians probably understood action on corruption to include the investigation of former vice president Joe Biden and his son Hunter Biden.

But don't forget about Vice President Mike Pence. The Washington Post reported overnight:

The timeline of events paints an exceedingly unflattering picture. We know that Trump personally intervened to delay U.S. aid to Ukraine, which was desperate for the American assistance. We also know that Trump soon after had a telephone meeting with Zelenksy in which the Ukrainian leader stressed the significance of the aid package, only to hear his American counterpart say in response, "I would like you to do us a favor, though."

Trump's wish list included, among other things, Ukraine taking law-enforcement action to undermine Joe Biden ahead of the 2020 election.

We now also know that in the wake of that conversation, it was Mike Pence who spoke with Zelenksy in person, reiterating Trump's expectations.

That's not a great position for the vice president to find himself in. Trump's actions are likely to lead to his impeachment, and it now appears Pence may have done something quite similar.

One of the most striking things about the Washington Post's report on this isn't just the top-line revelation, but also the behind-the-scenes drama -- because reading the article, it seems clear that there are factions inside the White House, one of which is eager to drag Pence into this mess, and one of which is scrambling to keep the vice president out of it.

The trouble with the defense from Team Pence is how underwhelming it is.

The Post article noted, for example, that officials close to the vice president "insist that he was unaware of Trump's efforts to press Zelensky for damaging information about Biden and his son." Or put another way, Pence told the Ukrainian leader that U.S. aid was on hold, and Pence pressed Zelensky about "corruption" concerns, but the Indiana Republican didn't fully understand the big picture.

There are problems with the defense. A top member of Pence's team, for example, was on the Trump/Zelensky call. Pence also had access to the transcript of that call soon after it took place. The Post also reported, "White House officials said that Pence probably would have received the detailed notes of the president's call in his briefing book on July 26," the day after the phone meeting.

What's more, the detailed call summary was likely part of the briefing materials Pence received before his in-person meeting with the Ukrainian president. The article added, "Officials close to Pence contend that he traveled to Warsaw for a meeting with Zelensky on Sept. 1 probably without having read — or at least fully registered — the transcript of Trump's July 25 call with the leader of Ukraine."

I did appreciate the use of the word "registered" -- as if Pence saw the document showing Trump pressing Zelensky on Biden, but the vice president didn't fully get it.

Team Pence will have to do better than this.