House Democrats anguished over President Joe Biden’s spiral are consumed by one question: Can anything save their chances of flipping the House? So far only three endangered Democrats have publicly called for Biden to leave the presidential race. But behind the scenes, the dozens of battleground members and candidates whose races will determine the House majority are in a “hair-on-fire” level of panic, in the words of one House aide. Battleground members have placed urgent calls to leadership and Biden’s team, commissioned new polls back home and even mulled sending a letter to Biden himself, according to more than a...