Bill Richardson, former Governor of New Mexico, is a friend of the Clintons. Recently Richardson went on a "diplomatic" trip to North Korea. Why? As then-Governor of New Mexico, he didn't really have much input in our relations with North Korea. I realize he was a former foreign diplomat, but there are tons of former foreign diplomats and they're not traveling to North Korea. He had to obtain permission from the White House and State Department in order to travel.
I put two and two together. This trip came at the very end of Richardson's term, so he wasn't just a private citizen going to North Korea; it provided him the opportunity to form official "diplomatic" relations. It will enhance Richardson's foreign policy cred even moreso. The State Department (i.e. Hillary) would not have ok'd this trip if he was going to run for POTUS on his own. She's building her brigade. If she runs, she could very well win the Democratic nomination. She could pick Richardson as her VP and use this trip as a promotion tool for him.
Given how volatile our relationship is with North Korea, can you imagine the State Department giving the governor of Nebraska, Idaho, Vermont, or any other state the ok to take a diplomatic trip there? No. Why would they even need to? Why would Richardson even need to unless he is planning on being appointed to a cabinet position again? So, that leads me to believe that the only reason Richardson went is because he's a friend of the Clintons. He's been a player inside the Beltway for over 20 years. This was a political favor for someone, probably several people: Richardson to Hillary, Obama to Hillary, and possibly a few more. It was a blip on the news cycle but I believe this trip is a big indicator that Hillary has decided to run.