Ever since the dawn of modern media and Teddy Roosevelt’s coinage of the term “bully pulpit,” political parties that don’t control the White House have struggled to match the agenda-setting power of the presidency. We’re living through an asymmetry that seems more daunting and profound than ever. President Trump has a feral, almost pathological genius for getting people to talk about him, and to a degree that his supporters find thrilling and his opponents find suffocating, he dominates the nation’s and the world’s attention.