Endorsements are sought intensively and appear to move fewer votes than they once did. The change follows from what an endorsement was originally for.
Endorsement was an information shortcut
A voter who knew little about a candidate could learn a great deal from discovering that a trusted local figure or organisation supported them.
The endorser had access to information the voter did not, having met the candidate, examined their record and assessed their competence directly.
That informational advantage was the source of the endorsement's value, and it has largely disappeared as candidate records and statements became directly accessible.
Trust in the endorsing institutions has shifted
The weight of an endorsement depends on the audience's confidence in whoever is giving it, and confidence in many traditional endorsers has declined.
Where an institution is viewed as aligned with one side, its endorsement conveys alignment rather than assessment, which is information the voter already had.
Some endorsements now function in reverse, mobilising opposition among voters who distrust the endorser more than they trust the candidate.
Organisational endorsements still carry resources
Backing from a membership organisation frequently comes with volunteers, mailing lists, funding and direct communication with members, which has effects independent of persuasion.
Those resources matter most in low-information contests where turnout is small and organised members constitute a large share of the electorate.
This is why endorsements retain more force in local and primary contests than in high-profile general elections.
Within-party endorsements do different work
In a primary where all candidates share a party label, endorsements from officeholders signal which contender the party's own network considers viable.
That signal reaches donors and staff more than voters, and its effect operates through the resources those groups then supply.
Where a party's own network is distrusted by its members, the same signal can be counterproductive, and candidates occasionally decline endorsements for that reason.
Timing changes the meaning
An early endorsement is a genuine risk taken when the outcome is uncertain, and it can shape the field by discouraging other entrants.
A late one, arriving after the result looks settled, conveys little and is generally read as positioning for the aftermath rather than as an attempt to influence it.
Distinguishing the two explains most of the variation in whether a given endorsement appears to matter at all.