Reacting to these three remarks, one attributed to Trump, one to a Trump ally, and one to his lawyers.

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Major US politician:
Current or former House representative, Senator, governor, WH cabinet member, or president
Current candidate (e.g. declared at time of assassination) who has reached double digits in their current race for one of these positions in at least one credible poll
In Trump's name:
Direct order from Trump
Trump, Trump cabinet member, or Trump "ally" (referred to as such by a credible media organization) charged in connection with the assassination
(Not going with convicted because who knows what future we'd be living in then -- but might N/A if the allegations seem bogus)
Person who is convicted of / pleads guilty to assassination admits to doing it in support of Trump's cause, or in what they interpret as Trump's interest (or credible media organization strongly suggests that this is the case)
2028:
Intended this to mean after another full presidential term has passed, so I'm also including the first 20 days of January 2029
Act, but not conviction, must be committed by this date
Open to criticism, this is a tough resolution criterion to nail.