You ask: In both of the sentences above, why can't we say "....might have..."?
I'll answer: Who says you can't? Let's try it, and see what happens:
“I thought she had a good chance to get on the medal stand,” Dunn said Monday. “Andif she got a good jump, I thought she might have a chance to win it".
That version seems grammatical, too.
Essentially, the speaker is saying:
If she had a good jump, she might have won.
There are many ways to say that, and you may not hear the most straightforward way of saying it the moment a microphone is thrust into a coach's face. So, the coach says,
If she got a good jump, I thought she might have had a chance to win [the race].
In this original, the words "if...", "I thought...", "might have...", and "a chance...," we are pretty well-nested in conjecture and conditional language. The result is a sentence where the word had could be omitted or included, and the sentence pretty much means the same thing, especially if you change the punctuation around:
"With a good jump," I thought, "She might have a chance to win the race."
The same holds for your first example:
Eddie didn’t talk much about it, but I thought she might have had a problem with alcohol.
Eddie didn’t talk much about it, but I thought she might have a problem with alcohol.
The phrase "I thought she might" puts the sentence in the past tense, so the had can be removed. If I remove that phrase, though, the had needs to stay in place:
Eddie didn’t talk much about it, but she had a problem with alcohol.
Remember, we are dealing with spoken words that were written down, not an author's polished work. A writer may have revised the sentence to read something more like this:
Eddie didn’t talk much about it, but I thought she had a drinking problem.
Once again, after the conditional language has been removed, the had is required. Also, just like last time, I can remove the had, particularly with a change in punctuation:
Eddie didn’t talk much about it, but I thought, "She might have a problem with alcohol."
The following three sentences mean different things.
If you had come tomorrow, I might have been able to help you.
This sentence is a counterfactual. It means that, because you came today instead of tomorrow, I can't help you. And there is no chance that I can help you if you come back tomorrow—you lost your chance for help by coming on the wrong day. Or maybe you have a deadline; tomorrow is too late.
If you came tomorrow, I might be able to help you.
If you come tomorrow, I might be able to help you.
These both mean that I can't help you today, but if you come tomorrow, there is a chance that I will help you.
The difference between them is in my perception of how likely it is that you will come back tomorrow. If I think it's very unlikely, I would use came. If I think it's very likely, I would use come. And for moderate likelihoods, either tense works fine.
Best Answer
We using might be able to if we have power to do this thing.
We using might have to if we predict what we probably need to do this thing.