It’s possible to have a strong hand and still overplay it. As Republicans see things, that’s what President Obama is doing in the “fiscal cliff” negotiations. In private conversation, some in the GOP appear a little sheepish about the fact that they once took the president seriously. Even though he had the upper hand after winning re-election, they thought he genuinely wanted to avoid going over the cliff and would negotiate in good faith. Then Obama sent Treasury Secretary Tim Geithner to Capitol Hill with a thumb-in-the-eye offer, and Republicans got the message. In subsequent days, Obama has not only …