Who will be the first sitting congressman/senator/governor to endorsed TRUMP?

[JMT]

Gov: Rick Scott
Sen: Steve Daines? (Kinda stumped on this one)
Reps: Steve King (IA-4)

Correct me if I'm wrong, but didn't Rep. King endorse Cruz?

Yes he did. And Daines endorsed Rubio

[JMT]

Nobody from my state.

Although that's because MA's only sitting Republican is Charlie Baker, who would never endorse Trump unless he wins the nomination.

I'm not even sure he would then. I doubt Bruce Rauner would either. They may be able to get away with quietly not endorsing since they're from safe D states where Trump (presumably) wouldn't spend much time.

I agree, I don't think Rauner or Baker will voluntarily endorse Trump. But I'm sure someone will try to ask them if they support Trump if he's the nominee, so it'll be interesting to see how they respond to that question.