WASHINGTON — Sen. Bernie Sanders’ ascendancy as Democrats’ leading presidential hopeful fueled growing unease as lawmakers openly expressed anxiety that the self-proclaimed democratic socialist could cost them House control and questions abounded over what party leaders should do. House Speaker Nancy Pelosi, D-California, projected calm — and neutrality — on Wednesday as she batted away reporters’ queries about whether it was time for her to try thwarting Sanders to protect her party’s majority. “We’re not going to lose the House,” she said.