Whoop-de-doo... endorsements mean little unless they have either an intensely loyal following in the party (Bill and Hilary Clinton) or a powerful organization (Tom Harkin in Iowa, Chuck Schumer in New York). As a result, Solomon Ortiz's support means little except that Texas might be Clark country come March 9, if he's even still around.

In places which still have machine style politics, the head of the local machine can still sway a lot of votes.
That's especially true if the endorsement is for an office that voters are not too concerned about.
During the era of the first Mayor Daley (1955-1976), many Chicagoans would ignore his endorsements for president or governor, but would blindly follow his recommendations for patronage rich offices like recorder of deeds, county clerk, or sheriff.

A somewhat different dynamic may exist in Texas.
Nobody expects a Democratic presidential candidate to carry the Lone Star State this year. So locals in some parts of the state, not too worried about who will eventually get the nomination, may be more willing to follow the recommendations of local party bosses whom they know and respect.