If no candidate gets a majority of the 538 electoral votes, a “contingent election” for President is decided in the House of Representatives, with each state delegation having one vote. A majority of states (26) is needed to win. Senators would elect the Vice President, with each Senator having a vote. A majority of Senators (51) is needed to win.
The risk of contingent election is increased by the presence of “third party” candidates that are capable of winning electoral votes, driving down the balance of electoral votes available to the two major parties below 538 electoral votes. For example, if the third party candidates won eight electoral votes, the two major parties could tie at 265 electoral votes each, triggering a contingent election. Similarly, if the third party candidate won eight electoral votes, one major party candidate received 266 electoral votes, and the other major party candidate received 256 electoral votes, a contingent election would be triggered.
House delegations can cast their vote for president from among the three candidates receiving the most electoral votes, while Senators are limited to the top two candidates in their vote for Vice-President.
In this partisan era, it is a reasonable assumption – at least to start – that the vast majority of members would vote along party lines.
As of late September, 2023, Republicans hold a 26-22 edge in House delegations. Two states, Minnesota and North Carolina, are evenly split.
However, it is the members of Congress elected in November, 2024, and seated in January, 2025 that would take on this responsibility.
Determination of the presidency could hinge on a single House seat. Which party controls the House always matters, but in the context of a contingent election, those stakes become monumental: The party with a majority of seats can set the rules that govern the contingent election. Republicans currently hold a narrow majority of seats in the 118th Congress, but Democrats could easily make gains in 2024.
In the contingent election context, which party controls individual seats takes on outsized importance since a single member could determine whether a state delegation registers support for one candidate or another, or fails to meet the threshold for any candidate. As a result, the majority party in the 119th Congress could have strong incentives to delay or refuse to seat members of the opposite party, if doing so could alter the outcome in pivotal state delegations.