Americans increasingly favor tougher gun laws by margins that have grown wider after a steady drumbeat of shootings in recent months, but they also are pessimistic that change will happen anytime soon, according to a new Associated Press-GfK poll. Nearly two-thirds of respondents expressed support for stricter laws, with majorities favoring nationwide bans on the sale of semi-automatic assault weapons such as the AR-15 and on the sale of high-capacity magazines holding 10 or more bullets.