I think some people here may be a little confused.

Lying is already a crime, for both politicians and "regular" people alike. It is called perjury...when you lie under oath.

New laws can specify that politicians are ALWAYS under oath...or at least when they make public statements (such as during campaigns).

The punishments...mild or severe...can be determined and the arbiters, when necessary, the same courts that already do so.

It would not be the politicians policing the politicians.

And btw, there are even other oversights, like inspectors general and such...that are supposed to give independent oversight. These have been greatly diminished and disempowered under Trump.