For a good long time during the George W. Bush and Obama presidencies, Paul Ryan was considered one of the intellectual leaders and shining stars of the Republican Party. Ryan, Mitt Romney’s 2012 vice-presidential running mate, was a stalwart advocate of lower taxes, entitlement reform and hawkishness on the deficit. Then Donald Trump arrived and blew everything up. A now 53-year-old Wisconsinite, Ryan, who served as speaker of the House from 2015 to 2019 before retiring to family life, think tanks, academia and corporate boards, went from policy captain to anachronism, his affable Reaganite focus on supply-side economics out of place on a remade political stage of continual conflict-baiting and culture-war outrage. Recently, though, Ryan has re-entered public life, though only partly of his own choosing. His behind-the-scenes concerns about the direction of Fox News — he’s on the Fox Corp board of directors — were put on display as part of the Dominion defamation lawsuit against the company. He is also trying to prevent the Republican presidential nomination from again being won by Trump, with whom he had a tortured if politically fruitful relationship, and he is touting a new book, “American Renewal: A Conservative Plan to Strengthen the Social Contract and Save the Country’s Finances,” which he edited with Angela Rachidi. “I always look at the glass as half full,” Ryan says about our current political moment, “but one of our biggest challenges right now is our fundamentally unserious politics.”