NEW YORK — Basking in loud chants of “Bernie’s back,” Democratic presidential candidate Bernie Sanders resumed campaigning weeks after being sidelined by a heart attack and told supporters he was ready to resume “the epic struggle” for the White House. Energized by thousands of backers gathered for a Queens rally, the 78-year-old Vermont senator said, “When I look at this huge crowd, brothers and sisters, I have no doubt that the political revolution is going to sweep this country, sweep Donald Trump out of office and bring the change that this country has long needed.” He said he was “more ready than ever to carry on with you the epic struggle that we face today.