If Trump will only do well where people vote, then he’ll lose large.
The people don’t vote at the convention; delegates do.
And the “politburo”, as you say, pick delegates in most places.
The convention is going to be full of party insiders. That’s the whole purpose of a convention.
No. If Trump wants to stay viable after round one, every delegate counts. He has to contest here. Can he win without those particular delegates? Sure. But he won’t win if he blows off contesting for delegates just because the insiders will have a say.
Oh well. This election is headed to the House of Representatives since we are going to have Trump and Bernie as 3rd party. And you are going to have a democratic house because GOPe chose to blow itself up.
As noted above, every candidate has limited resources, and has to pick and choose which delegatations and delegates to woo. He doesn't have to contest everywhere, and as you concede, he can win without personally wooing Colorado delegates this weekend.