Trump, while now more popular with Republicans, may not be electable with the rest of US voters

In a piece in The Atlantic, Ronald Brownstein reports that Donald Trump today is much more popular among Republican voters than he was several months ago. However, he remains widely unpopular among Democrats and independents, and were he to win the Republican nomination his inability to gain the votes of non-Republicans would likely lead to his defeat:

A widen­ing dis­tance between per­spect­ives about Don­ald Trump among Republicans and all oth­er voters—the “Trump gap”—presents GOP lead­ers with a conun­drum as the primar­ies approach. The phe­nomen­on can be charted across a series of na­tion­al polls, from which a con­sist­ent pat­tern has emerged in at­ti­tudes toward the GOP front-run­ner since he entered the race last sum­mer.

Re­pub­lic­an par­tis­ans and some oth­er con­ser­vat­ive-lean­ing con­stitu­en­cies are demon­strably warm­ing in their at­ti­tudes to­ward the blustery busi­ness ex­ec­ut­ive. But views of Trump gen­er­ally re­main stag­nant, or are even de­teri­or­at­ing, among adults who identi­fy as Demo­crats or in­de­pend­ents.

While Trump’s inability thus far to please non-Republicans looks costly, the leading Democrat, Hillary Clinton, has her own favorability problems, though they are not as bad as Trump’s:

What makes this pat­tern es­pe­cially fraught for GOP strategists is that Hil­lary Clin­ton, the overwhelming  fa­vor­ite for the Demo­crat­ic nomination, also faces very sticky negative perceptions among voters out­side of her par­tis­an base. Yet for all of Clin­ton’s dif­fi­culties with in­de­pend­ent voters and oth­er swing con­stitu­en­cies, Trump’s stand­ing among the same groups usu­ally ranks lower in the same polls.

Brownstein reports that Trump has been increasing his popularity among GOP voters:

The mag­nitude of the change among Re­pub­lic­ans is even more ap­par­ent when con­sid­er­ing Trump’s net fa­vor­ab­il­ity: that is, the dif­fer­ence between the share of Re­pub­lic­ans who view him fa­vor­ably and un­fa­vor­ably. In the CNN/ORC poll, Trump’s net fa­vor­ab­il­ity has jumped from 9 to 43 per­cent­age points; in Quinnipiac polls, he’s moved from a net neg­at­ive rat­ing of 18 points to a net positive of 33; and even in the NBC/WSJ sur­vey, his net pos­it­ive rat­ing has nearly tripled from 9 to 25 per­cent­age points.

Because Hillary is hardly beloved, the contest in November may come down to which candidate can get his or her voters to show up in the polls, while those who don’t like either choose the lesser of two evils:

A race between two can­did­ates la­bor­ing un­der such cloudy pub­lic as­sess­ments might turn on which could do more to re­verse the neg­at­ive judg­ments evid­ent today. But it might also prove a uniquely neg­at­ive and bruis­ing con­test de­cided by which con­test­ant can more ef­fect­ively re­in­force the gap between their op­pon­ent’s strong stand­ing among their par­tis­ans—and far more tenu­ous po­s­i­tion with everyone else.