In private, President Trump spent much of the past week brooding, as he often does. He has been anxious about the Russia investigation’s widening fallout, with his former campaign chairman standing trial. And he has fretted that he is failing to accrue enough political credit for what he claims as triumphs. At rare moments of introspection for the famously self-centered president, Trump has also expressed to confidants lingering unease about how some in his orbit — including his eldest son, Donald Trump Jr. — are ensnared in the Russia probe, in his assessment simply because of their connection to him.