Trump was easily unnerved. Possibly the worst quality to have in a president.

[Yavin4]

Yes, Trump started off the debate well-prepared, but as soon as Hillary questioned his business acumen, he was done. He became unglued during and after the debate.

As president, we've been spoiled rotten by Obama's cool under fire. Hi focus never deters on what he has to accomplish even while everyone, left and right, were screaming at him.

How would Trump fare with a collapsing economy, a swine flu outbreak, an oil spill off the Louisiana coast, Somali pirates taking U.S. hostages, the hunting of Bin Laden, etc., etc., etc.

These are big events that can unnerve even the best of us. Imagine Trump dealing with these things when he cannot handle someone questioning his wealth!

--Edit to Add--
A president's primary job is as a crisis manager. Budgets, taxes, spending, laws, etc., that's Congress' job. it's the president who has to keep shit together when shit goes down.

[hopeforchange2008]

1. But, but - he has the winning-est temperament!!!

[FuzzyRabbit]

2. Imagine Trump as president during the Cuban missile crisis.

If Trump had been president in October 1962, the earth would have been a burnt out cinder 54 years ago.

[MFM008]

3. He panicked

And was nearly hysterical....

[MyNameIsKhan]

4. Remember he was sniffing very hard in first 20 minutes, trying to keep his cool, he must have been

told to breath, as soon as Hillary got under his skin, he gave and started jumping all over the place, he statements became incoherent. I feel Hillary has so much more material for second debate, thanks don the con, that he is toast. His advisors know this that is why they are thinking to back out.

Third debate is his Fox friend so he may take the bait. But if debates are not going help him, there is no reason to come.