WASHINGTON – On both economic and national-security fronts, President Barack Obama is giving ground and crossing swords with political allies. Caught in the worst economic downturn in generations, Obama has had to temper his stance on trade and lower his expectations for trimming charitable tax breaks for the wealthy and for taxing greenhouse-gas polluters. He's not the first president to be pulled toward the political center after being elected. But the recession and two wars abroad put him in a particularly tough spot — with smaller margins for error. With the deficit mushrooming, lawmakers in both parties are worrying more...