Julián Castro quit the 2020 Democratic primary.
The dropout comes just weeks to go until votes begin.
Business Insider says he had trouble getting name recognition, in part because of DNC debate eligibility requirements.
Castro is now a sought-after endorsement.
He is now on top of any Vice Presidential contender list.
Some candidates will benefit from Castro's departure.
A third of Sen. Amy Klobuchar's supporters like Castro as well as a quarter of Mayor Pete Buttigieg's.