Structural Notes on the 2020 Campaign: Trump Now Beset by Three Challengers: Attacking from His Left Is Former Gov. William Weld, Representing New England Rockefeller-Style Liberal Republicans, Horrified by Don’s Hooligan Behavior; Former Rep. Joe Walsh of Chicago Is Voice of Midwest Tea Party Extremists, Attacking Don from His Right; Classic Reactionary Former Gov. Mark Sanford of South Carolina Condemns Don for Deficits, Debt, And Spending, Ominously Foretelling Worst Economic Crisis Since 1930s; None Can Win, but They Can Get Enough Trump Voters to Stay Home, Closing Door to Dictatorship in 2021; GOP’s Clever Trick of Calling Off Primaries Only Leads to Extinction by Other Paths