Better would be to require the election to fill a vacancy to be held within 60 days. Congress clearly has authority to pass such a law under the time, place, manner of elections.
Actually it took the original language from Article I, Section 3, and replaced legislative election with popular election. The original language includes a provision for appointment by the governor when the legislature was not in session.
It was inconceivable that a legislature would go two years without meeting, and with Congress only meeting a few months per year, the legislature could often elect the replacement the senator who would serve.
The Senate was strict about enforcing the constitutional provisions on vacancies. If a legislature failed to choose a new senator, the temporary appointee of the governor would end his service at the time the legislature went into recess. If the legislature was in session at the time of a vacancy, the governor could not appoint a temporary replacement, even if the legislature was unaware of the vacancy.
The purpose of this language was to prevent Congress from directing where the legislature met, in effect dictating the location of the State capitals. It illustrates how extensive the powers under the time, (place), manner clause are - Congress can legislate in all matters except one very particular area where they would in effect be legislating something that would grossly interfere with the state government.
The provision is now superfluous, since Congress could probably legislate the location of polling places under the 14th Amendment, or at least keep States from making it difficult to vote.
The temporary appointment power is liked by the state
government because it takes power away from the voters. Elected government officials are inherently anti-republican. Their only concern about the expense of an election is what it would do to their campaign expenses.
