The first major client for the web development firm was El Paso’s Hunt Companies, owned by local construction magnate Woody Hunt.

Mr. Hunt, whose firm is among the nation’s largest developers of military housing, was friendly with Pat O’Rourke since both men were El Paso teenagers. Mr. Hunt became one of Beto O’Rourke’s most reliable business and political benefactors.

Since Mr. O’Rourke first campaign for Congress, Mr. Hunt has donated $4.2 million to Republican candidates for federal office and committees and $141,000 to Democrats.

In Texas he has given $3.3 million to Republicans seeking state office and $143,000 to Democrats—nearly all of which went to candidates from El Paso. Mr. Hunt gave the maximum contribution to both of Mr. O’Rourke’s re-election campaigns.

Along the way Mr. O’Rourke often reflected Mr. Hunt’s priorities.