WASHINGTON — House Republicans narrowly pushed through a bill on Thursday that slashes billions of dollars from the food stamp program, over the objections of Democrats and a veto threat from President Obama. Enlarge This Image Doug Mills/The New York Times The bill passed narrowly despite efforts by the House minority leader, Nancy Pelosi, who spoke at a news conference on Thursday. The vote set up what promised to be a major clash with the Senate and dashed hopes for passage this year of a...