By CALVIN WOODWARDWASHINGTON (AP) â¿¿ Absent a magic potion or explosive economic growth, it was all but inevitable President Barack Obama would have to break some of his campaign promises to keep others. If there's one thing that distinguished them besides their ambition, it was their incompatibility. Cut a staggering $4 trillion from deficits while protecting big benefit programs, subsidizing more health care, plowing extra money into education and avoiding tax increases on everyone except the rich? Not on this Earth. The postelection reality is starting to shake out now, though how it will all settle can't yet be known. To reach for his promised deficit reduction, Obama has proposed breaking his tax promise. Toward the same end, his pledge from four years earlier that he wouldn't trim cost-of-living benefits in Social Security has given way to a proposal to do just that. None of that might happen. Republicans, who oppose tax increases, and Democrats, who object to curbs on entitlements, could block his path and in doing so save Obama from breaking his own promises. If they do, though, that big pledge to bring down deficits by $4 trillion would surely have no hope at all. That's the overarching dilemma in a catalog of campaign promises facing varying prospects over the next few years. Obama is driving toward success on his energy goals. He's got a decent chance of achieving an immigration overhaul. Activists who once ridiculed his promise to be a "fierce advocate" of gay rights say he's come around and become just that. Much else is bogged in the budget swamp or is a nonstarter for one reason or another. Anything costing big money comes with big obstacles, and one promise that cost relatively little, gun control, is dust. Yet Obama, in powering through with his health care overhaul, financial regulation and stimulus spending in his first term, has shown that tough causes aren't always lost ones.