Donald Trump is the first candidate ever to run for president in the last 40-plus years who has not released his tax returns, so everything he says about charity or anything else, we can't prove it.

It is essential that America's word be good.

I think Americans have every reason to be worried about ISIS and the network of terrorist groups, because they have proven to be sophisticated and effective in wreaking violence and murder in many parts of the world, including in San Bernardino with their somehow connected radicalization of that couple there.

Standing up for America, investing in America, will pay off.

There is no disagreement between us [with Bernie Sanders ] on universal coverage for health care, the disagreement is where do we start from and where do we end up.

I think that there is a strong argument that our [USA's] leadership, our strength, our influence begins with having an economy that is producing good jobs with rising incomes, and I see the connection there.

No nation can meet the world's challenges alone.