Now that he has conclusively won the New Hampshire primary, it looks far-fetched that Donald Trump’s one remaining rival, former U.N. Ambassador Nikki Haley, is going to swoop in and take the Republican presidential nomination from him. That means that Democrats need to move past their justifiable shock and incredulity that Trump may be president again and get real about crafting a strategy to beat him in November’s general election. If you believe the polls, Biden is not just losing but is in arguably the worst position of any incumbent seeking reelection in the modern era. To turn it around,...