Bizarre headline. He didn't "win" 42%, he received 42% of the votes, yet still lost the primary. I didn't read the rest of the article and don't know about his story, so can't judge further, but this is a basic clarity issue that should be fixed.
He won 42% (of the votes); that use of win as a transitive verb is ordinary in English. Had the headline said "wins with 42%", that would be totally different — the verb would be intransitive, and the headline would be simply false.