Should there be a mechanism for government to continue if no election can be held?

[President Johnson]

Inspired from the What-if thread about how 2020 would have turned out if Yellowstone erupted rather than Covid emerging. Should there be a clear constitutional mechanism to continue the US government in case an election can't be held? Such circumstances may actually arrive at some point in time, for example if Yellowstone indeed erupts months before the presidential election. Even before the midterms it could be problematic since all congress(wo)men are up for election. How should said mechanism look like? I think it should definitely be made sure it can't be abused by a president with autocratic tendencies whose objective is only to stay on power.

Other countries have various laws and constitutional amendments in the books that prevent such a government crisis. In Germany for example the legislative term could be extended with a two-thirds majority. Even without the extension, the cabinet could serve on an acting basis for an unlimited amount of time.

I know that theoretically the president pro term would take over after January 20 depending on composition of the newly 66 member senate. But I guess that wouldn't work out very well; and the House has no members at all.