On a certain level, it makes perfect sense to appoint the useless, performative Rep. Marjorie Taylor Greene to a useless, performative impeachment trial. But ultimately, it shows just how little regard Speaker Johnson has for the branch of Congress he supposedly leads.
For one thing, Greene's appointment comes a week after she threatened to remove Johnson. The Independent, which reported on her appointment, noted that no Republicans have signed on to her motion to vacate, i.e. remove Johnson. If anything, her move angered her fellow Republicans to the point that they attacked it on conservative media.
MTG's appointment may quell her desire to oust Johnson but it will probably do nothing to quell the intra-party animosity among the House Republicans. As The Independent noted, the motion to impeach Department of Homeland Security Alejandro Mayorkas failed the first time, then passed the second time by one vote, with three Republicans voting with Democrats against it.
On top of all that, the impeachment is dead on arrival at the U.S. Senate. There's no way Mayorkas will be convicted by the required two-thirds majority in a Democratic-controlled Senate.
In fact, Senate Majority Leader Chuck Schumer could hold a vote to dismiss all the charges immediately upon their arrival, without any trial. That would not only avoid a big waste of time but also deprive the troll otherwise known as Marjorie Taylor Greene a spotlight you know she'd give up her motion to vacate for.
