I think you have hit the nail on the head here. If Trump wins, Cruz and Kasich's presidential chances are over forever and their chances for other high office are diminished. If Trump loses, Cruz and Kasich will be blamed and the result will be the same.
The smart thing would have been to urge others to vote strait R or say nothing at all. In my opinion, Cruz and Kasich have both ended their presidential chances forever.
While we agree on the first part, if Trump wins it will be because of two factors. Hillary is about the sleaziest and most patently unlikable criminal to run for public office since Marion Barry, and it will be a sad commentary on a hopefully conflicted electorate as well.
As far as ending Cruz or Kasich political careers, I think not.
If Trump wins, he has four years to make a complete mess of things, and from just what he has done creating unity and all that in the last four months, I would wager that (if there hasn't been an extensive thermonuclear war), he will have a legacy of screwups that will rival or exceed those of any sitting president. He will, inevitably and to the great consternation of those who have sold their souls to stand with him, have damaged the Republican brand, but by association ended not only his own political career but those of those who went out of their way to support him. Assuming, that is, that he takes no extraordinary measures to retain power, at which point there would be a 'fundamental change' in our system of Government, and not a return to the Constitutional Republic we crave.
I don't see that as damaging to the man who would not go along to get along.
If Trump loses, Cruz will have stood steadfast in the breach and called for Constitutional principles and freedom, for voters to vote their consciences, and essentially have made the statement that this was One Big A$$ed Mistake America, all over again.
Essentially, again, not damaging to the man who would not lay his reputation down to support a "LOSER", as that candidate might characterize the situation if applied to someone else.
Integrity and character count for something, and Cruz will have displayed those. By telling those assembled and watching or reading his comments to vote their conscience up and down the ticket, Cruz told no one how to vote, only to vote for the candidate that they felt worthy of their vote, who aligned with their personal values. He did not say to NOT vote for anyone in particular, just as he did not say to VOTE for anyone in particular. For those of us who viewed the continuous attacks on his honesty, integrity, marital fidelity, his spouse and even his relationship with his children, and his father as well, I'd say Cruz showed remarkable restraint, simply keeping it about the country and not specific people, including himself.
YMMV, but I think Ted Cruz will be around for a while. I fully expect that Donald Trump will, one way or another, continue to seek to harm Senator Cruz, and will likely contribute to his political opponents in the future.
Lies have a way of being debunked, and they have been. All that remains is for the purveyors of those lies to quit repeating that which they should by now know not to be true before the last person with the facts steps in and straightens out the record. Distortions of fact are often removed by the lens of time, so I have confidence this will occur, especially in the face of either failure of the candidate at the polls or failure if elected to fulfill the promises made to his sycophants.
Cruz stood fast. Whether people agree or not they either respect that or betray their own guilt by attacking it.