Tell me you don't understand politics without telling me you don't understand politics. If he had done it in his first week in office we would have all forgotte

Tell me you don't understand politics without telling me you don't understand politics. If he had done it in his first week in office we would have all forgotten by now and the republicans could sour the pot drastically in the intervening two years. By doing it now, he gains broad appeal going into an election season so that he is potentially enabled to enact more beneficial policies down the line. Never forget that the republican party is working against the interests of the people and the party that opposes them and will do whatever they can to twist public perception to their side. Being purely sincere and principled means getting routed by people who work against your sincerity without any regard for principle. It can be both a sincere and principled choice and an action taken based on careful political calculation. In fact, I'd say that if it really were sincere and principled, it should be as calculated as possible for maximum beneficial effect.