It is rather a plain construction which is very similar to "It ain't over until it is over". She wants to emphasize the fact that she didn't take any postion on it until recently.
Plain translation would be:
"I never expressed my opinion on Keystone in my life time. I recently took a position on Keystone and that is the only position that I took on this issue. There is no flip-flopping on this. It wasis my husband who might have supported supported it. Not me!!! Please don't confuse me with my husband!!!"
The link shows what Bill Clinton remarked regarding the Keystone pipeline project in 2012 when Hillary was Secretary of State.