Louis C. Wyman (R–New Hampshire) was declared the victor of the US Senate contest in 1974 in New Hampshire by a narrow margin on Election Day (355 votes). A first recount gave the election instead to John A. Durkin (D–New Hampshire) by ten votes, but a second recount swung the result back to Wyman by only two votes. The state of New Hampshire certified Wyman as the winner, but Durkin appealed to the Senate, which had a sixty vote Democratic majority. The Senate refused to seat Wyman while considering the matter. After a long and contentious debate in the Senate, with Republicans filibustering attempts by the Democratic majority to seat Durkin instead, a special election was held, with Durkin winning handily and becoming Senator.—Wikipedia

I suppose the 1974-1975 debate over seating a Senator from NH took place in the newly elected Senate . Democrats were in the majority before and after the 1974 election; Mike Mansfield (D-MT) was the Majority Leader during both sessions.

The 1974 precedent–a special election to settle a near tie–seems good to me. The filibuster rule contributed played an important role. Under different circumstances, the precedent might not hold.

• The lame duck Senate in 2020 will know how the 2020 election went.
• McConnell is ruthless, but it isn’t clear to me what he might do to cling to power if Republicans don’t have a clear majority in the new Senate.
• The new Senate will adopt rules and choose a leader. Does the former leader retain the position until a new leader is chosen? Could newly elected Senators be excluded from these votes, or defeated candidates be allowed to vote?
• In 1974, there was no dispute over election procedures–hanging chads, mail-in ballots, illegal voters.
• Might there be another lengthy debate over seating; might one party or the other appeal to the courts?
• If there were a tie in the Senate, the Vice President would cast the deciding vote.

An unprecedented partisan outcome would be bad for democracy.