"Do we need a constitutional amendment to prevent it?"

No.

Shouldn't this be something that the individual states decide for themselves?

It really shouldn't be anyone else's decision besides the two people wanting to be married. What the hell business is it of the president's -- or the governors' or mayors' -- that two people want to join in matrimony?

Isn't Bush trying to make a political issue out of something that in the grand scheme of things is relatively unimportant?

Yes.

Isn't he pandering to the extreme conservatives and the religious right?

Yes. And I really don't know how that is supposed to help him. He should be leaning a little to the left if he wants to be re-elected, I think.