From Jonathan Bernstein:
Now is the time to finally fix the presidential order of succession.
The order of succession outside of the vice president is determined by legislation, not the Constitution, and it’s changed several times over the years. The current law has several problems. By inserting the speaker and the Senate president pro tempore into the line of succession, the law raises the possibility of a partisan incentive to remove the elected officials, at least during times of divided government. That’s a terrible idea. The president pro tempore of the Senate, regardless of party, has no business being involved with this at all — they get that distinction by having the most seniority, which means that half the time it’s someone long past their prime. And there has been more than one recent senator with the job who wasn’t remotely capable of handling normal Senate duties, let alone the presidency.
Along with whatever else is done, they should make the line of succession temporary, and a new president should be elected by the people to fulfill the previous president’s term after a relatively short period of time.