Any so-called leader who does not take this issue (climate change) seriously or treats it like a joke is not fit to lead

I think there are a whole host of things that are civil rights, and then there are other things - such as traditional marriage - that, I think, express a community's concern and regard for a particular institution.

Yes, our greatness as a nation has depended on individual initiative, on a belief in the free market. But it has also depended on our sense of mutual regard for each other, of mutual responsibility. The idea that everybody has a stake in the country, that we're all in it together and everybody's got a shot at opportunity. Americans know this. We know that government can't solve all our problems - and we don't want it to. But we also know that there are some things we can't do on our own. We know that there are some things we do better together.

I opposed the Defense of Marriage Act in 1996. It should be repealed and I will vote for its repeal on the Senate floor. I will also oppose any proposal to amend the U.S. Constitution to ban gays and lesbians from marrying.

We remember the specter of sectarian violence -- al Qaeda's attacks on mosques and pilgrims, militias that carried out campaigns of intimidation and campaigns of assassination. And in the face of ancient divisions, you stood firm to help those Iraqis who put their faith in the future.

If we don’t uphold our Constitution and our values, that over time, that will make us less safe and that will be a recruitment tool for organizations like Al Qaeda. That’s what I have to keep my eye on.

We seem to have trouble with [critical thinking]. And our political system doesn't help.