Heading into Wednesday night’s Republican debate at the Ronald Reagan Presidential Library, erstwhile front-runner Jeb Bush faces escalating pressure to be uncharacteristically combative toward Donald Trump, whose flair for showmanship and red meat, right-wing rhetoric has catapulted him to the top of the 16-candidate pack. While Trump had already seized the lead in national and early-state polls by the time of last month’s showdown in Cleveland, this time is different: With Trump having withstood months of withering criticism for inflammatory remarks that would have sunk any other candidate, the conventional wisdom that The Donald would inevitably self-implode before a single vote is cast looks far less tenable than it did when Trump launched his campaign in June.