The speaker is mounting a multi-front rebuttal to the billionaire’s criticism — and trying to keep the backlash contained.Mike Johnson has spent his 19 months as speaker forging a close relationship with President Donald Trump — in part to avoid the social-media bombshells that derailed so many Republican priorities during Trump’s first term.Now he has to deal with another, perhaps even more unpredictable online bomb-thrower.Elon Musk’s decision to launch a sudden scorched-earth campaign against the GOP’s domestic-policy megabill has forced Johnson into a sudden scramble to save the centerpiece of the Republican legislative agenda.Starting in the moments Tuesday after Musk...