...what the lefty liars are saying. His argument is that the president is immune from prosecution for acts that fall within his official capacity as president -- a standard of immunity, by the way, which also applies to both the judicial and legislative branches.

This question was adjudicated decades ago with respect to a case involving Nixon and CIVIL (not criminal) liability, and it was decided that the president has ABSOLUTE immunity from civil liability related to his official acts. Trump is arguing that the same immunity standard should and does apply to criminal liability. This question has never arisen before because we've never had a regime as corrupt as the Biden regime waging lawfare on its predecessor/current election opponent, forcing SCOTUS to provide an opinion on the matter.

There are multiple reasons why this standard of immunity should exist, including separation of powers issues and simple logistical issues, the latter being exemplified by exactly what is happening to Trump right now -- i.e., a spiteful, corrupt, partisan successor administration is trying to punish him, undercut the next election and corrupt our politics generally via lawfare by attempting to criminalize his actions as president. Obviously, it would have a chilling effect on our politics and presidency if presidents had to labor under the concern that they could be jailed in the future for carrying out the responsibilities of their office.

All this begs the question, of course, of whether the acts with which Trump is charged were actions taken within the scope of the presidency. He would argue yes, while Smith would argue no. In my view, the likely outcome of this appeal will be that SCOTUS will apply the same level of criminal immunity to the president as it does to civil liability, but probably will not decide whether Trump's actions were official. Thus, the case will get kicked back to Chutkan's court for an evidentiary hearing on that topic, where she will, of course, find in favor of Smith, and then the entire appeal process will begin again.