The situation Mike Pence faces as Vice President after less than a month in office is that he must be starting to realize that he will become President at some point during this term.
The same situation faced Gerald Ford in December 1973, when he became Vice President under the 25th Amendment, the first such use of that amendment just passed six years earlier.
Ford knew that Richard Nixon was in trouble, and Mike Pence knows Donald Trump is in trouble.
Both Ford then and now Pence must “walk on eggs”, and be careful about what they say and do, in order to avoid any untoward indications of interfering with the procedures used to judge whether the President they serve is someone who should be removed from office.
But at the end, it is likely that Mike Pence will feel a need to utilize Section 4 of the 25th Amendment, to remove Donald Trump from office as a danger to national security and stability, due to reckless and unstable behavior in the Oval Office.
Both Ford and Pence owed their elevations to the Vice Presidency to their Presidents, but just as Ford was prepared to take over the Presidency. so will Mike Pence be ready when the time is right. which is likely sometime later this first year of the Trump Presidency, which seems assured to be abbreviated to probably more than James A. Garfield (199 days) but much less than Zachary Taylor (492 days).