Inside the Republican Party's Desperate Mission to Stop Donald Trump

Despite all the forces arrayed against Mr. Trump, the interviews show, the party has been gripped by a nearly incapacitating leadership vacuum and a paralytic sense of indecision and despair, as he has won smashing victories in South Carolina and Nevada. Donors have dreaded the consequences of clashing with Mr. Trump directly. Elected officials have balked at attacking him out of concern that they might unintentionally fuel his populist revolt. And Republicans have lacked someone from outside the presidential race who could help set the terms of debate from afar. Should Mr. Trump clinch the presidential nomination, it would represent a rout of historic proportions for the institutional Republican Party, and could set off an internal rift unseen in either party for a half-century, since white Southerners abandoned the Democratic Party en masse during the civil rights movement.