you are a Republican so indoctrinated in party loyalty that, no matter how you despise a candidate, no matter whether you will actually vote for that candidate, you must publicly display "unity" and pledge your loyalty to the party and the party's nominee.
My own Republican House Rep is doing just that; he's used strong language to condemn Trump, but hasn't taken his endorsement back. That's when an endorsement is not an endorsement, since you asked.
The same thing happens in the Democratic Party, and right here at DU. You know. The people who rush around demanding loyalty oaths a year ahead of an election. The people who will excuse any candidate of anything during campaign season, as long as that candidate has a "D" next to his or her name. The same people who find no contradiction in embracing the positions of a D candidate or an elected D that, before campaign season, they were solidly against, but now twist themselves into pretzels to rationalize their "evolution."
It's a pot and kettle thing.