For nearly four years, Republicans have delved into the darkest corners of Hunter Biden’s life, seeking to tie his troubles to his father, President Biden. But as the younger Biden stands trial in Delaware on gun charges, the case’s glaring political contradictions have rendered the G.O.P. largely mute, from former President Donald J. Trump on down. It stands to reason: The baseless claim that the Biden Justice Department is running a political persecution of Mr. Trump is somewhat undermined...