"Oh, shut up": Maine Senate debate gets testy

Maine Republican Sen. Susan Collins and her Democratic challenger Troy Jackson were sparring in a testy debate Thursday night when a protester loudly interrupted them."So this is obviously one of Troy's supporters," Collins said."Oh, shut up," Jackson shot back. "I don't even know that kid."Why it matters: Collins and Jackson are competing in one of a handful of races that will determine the Senate majority.The two have traded barbs in a series of tense debates, but this was the first time they sounded like children arguing on a playground.Zoom in: At another point in the debate, Collins, who'