Deflated Republicans were embarking on a period of introspection and blame on Wednesday after Herschel Walker, Donald Trump’s handpicked candidate, fell well short in his effort to capture Georgia’s Senate seat. Walker’s failure in the runoff against the incumbent Democrat Raphael Warnock was the most recent of a long list of misfires in the midterm elections for extremist candidates endorsed by the former president, who announced his latest run for the White House last month. It secured Democrats a 51-49 majority in the Senate, leaving Republicans powerless to block key elements of Joe Biden’s agenda, especially judicial appointments, for at...