States don't have to change the laws, the Delegates can vote for whomever they want. Republican rules bind them to the first Ballot, but there could be a situation where none of the candidates have the majority. The second round they can vote for anyone, whether they ran in the primary or not. I don't assume the dems have the same rules, but if they do they have super delegates that have more votes than the rest and can decide against the will of the partys electorate.
Democratic Party rules governing vacancies See also: Democratic presidential nomination, 2020 Under Article 2 of The Bylaws of the Democratic Party, the Democratic National Committee (DNC) has the responsibility to fill vacancies in presidential and vice presidential nominations between national conventions.[3]
In the event of a vacancy on the national ticket, the chairperson would call a special meeting. Under Article 2 § 8(d), questions before the DNC, with some exceptions otherwise outlined in the charter and bylaws, are determined by a majority vote of the DNC members who are present and voting by proxy. The bylaws also state that voting to fill a vacancy on the national ticket must proceed in accordance with procedural rules adopted by the Rules and Bylaws Committee and approved by the DNC.[3]
The ballotpedia link also shows how the GOP can do the same thing with their rules. These are likely in place to prevent a death/assassination from giving a single party the win.
States don't have to change the laws, the Delegates can vote for whomever they want. Republican rules bind them to the first Ballot, but there could be a situation where none of the candidates have the majority. The second round they can vote for anyone, whether they ran in the primary or not. I don't assume the dems have the same rules, but if they do they have super delegates that have more votes than the rest and can decide against the will of the partys electorate.
See James Polk
https://www.washingtonpost.com/wp-srv/politics/campaigns/junkie/archive/junkie061899.htm
Techno_Fog & Ballotpedia have some info on this.
2022 Rule Update: https://x.com/Techno_Fog/status/1725205163017707945
2020 Rule Update: https://ballotpedia.org/State_laws_and_party_rules_on_replacing_a_presidential_nominee,_2020
The ballotpedia link also shows how the GOP can do the same thing with their rules. These are likely in place to prevent a death/assassination from giving a single party the win.