A team from the Cicero Institute, founded by billionaire Joe Lonsdale, flew to Indiana this year to help pass a law making it a crime for homeless people to sleep on the street. After previous failures, the ban passed just before the legislature adjourned, aided by Cicero lobbyists and analysts. The group has commandeered Republican homelessness policy.

Mr. Trump issued an executive order that fully reflected Cicero’s agenda. The administration aims to transform federal aid away from housing subsidies and toward forced treatment of substance abuse or mental disorders, arguing that the federal Housing First policy neglects root causes. 21 states have considered Cicero-backed laws, and 16 have passed them.

A co-founder of Palantir, Mr. Lonsdale, 43, brings vast wealth but no experience with homeless services. He argues that a corrupt “homelessness industrial complex” dominated by liberal groups wants to increase homelessness to discredit society. Cicero has helped make Housing First a conservative epithet, showing how rich donors can shape the safety net.