Why are 1st half spreads often far from half the game spread? For example, the Broncos are -8 for the game and -6 for the first half. I couldn't resist taking Chargers +6 for the 1st half and Broncos -8 for the game. It just seems like the odds are in your favor with bets like that.
Because teams often leading by more than 1 score play prevent at the end of the game allowing for easier scores / backdoor covers. This is why the half-time spread is usually more than half of the total spread like in this case.