The big threat to Hillary Clinton's campaign isn't coming from a competitor. It's coming from an issue. And it's coming now, long before the first primary. Will she be for or against giving President Barack Obama fast-track authority to negotiate trade deals?

Fast track gives a president the power to make trade deals that cannot be amended by Congress. All Congress can do is accept or reject the agreement. Other countries, say fast-track supporters, won't negotiate with Washington if they know that Congress can amend any deal they agree to.

If he gets fast-track authority, Obama will be in a position to conclude negotiations for the Trans-Pacific Partnership, a mammoth free-trade deal among 12 Pacific Rim nations that represent 40 percent of the world economy. Obama embraced the deal saying, "We have the opportunity to open even more new markets to goods and services backed by three proud words: Made in America."