WASHINGTON — Sen. Joe Manchin has said he’ll oppose an economic measure he’s been negotiating with Democratic leaders if it includes climate or energy provisions or higher taxes on the rich and corporations, a Democrat briefed on the conversations said late Thursday, delivering a stunning blow to one of the party’s top election-year priorities. The official said Manchin told Senate Majority Leader Chuck Schumer, D-N.Y., on Thursday that he will only support a new measure if it is limited to curbing pharmaceutical prices and extending federal subsidies for buying health care coverage.