How binding are these anyway? I mean, wasn't Snowe definitely running in 2012, until she didn't?
I personally consider them truly "official" when the senator makes some type of official statement along with a press release that says they're running for reelection. Some one-off comment in an interview or a quick sound byte I don't really consider official.
I seem to recall Saxby Chambliss, Max Baucus and Mike Johanns all saying at some point or another in 2012 that they would definitely seek reelection, only to go back on it later (Didn't Johanns even hint that he was running for reelection about a month before he announced his retirement?)