Photo: Elizabeth Frantz/REUTERS

President Joe Biden walked before a row of flags and took his place at a lectern stamped with the presidential seal. A few feet in front of him, thin panes of teleprompter glass, programmed with prewritten remarks, were positioned to meet his stare as he spoke into a microphone that would carry his voice through a soundsystem. His White House press secretary looked on. So did several senior White House officials. Anxiety clung to the humid summer air. What the president was about to say might determine the future of his presidency and perhaps the Republic…