Rush never declares—which is smart. But I get your point. The strongest hint of an endorsement I ever heard him give was for Governor Scott Walker.
He was very good at talking up candidates without overtly endorsing them.
Especially Romney. Limbaugh was all over Romney years ago. And I heard him talking up Kasich more recently. As far as I’m concerned it has the same effect as an outright endorsement. Maybe even more potent.