four years ago, mitt romney, the republican presidential nominee, won the first fall debate with a smoothly delivered promise of cooperation. while president obama had rebuffed republicans, mr. romney would <u+201c>work on a collaborative basis<u+201d> with democrats. that upbeat message, fanciful then, has now lost any veneer of plausibility. as donald j. trump approaches his second debate with hillary clinton, republicans are struggling more than ever to work with each other, much less the other side. instead of negotiation, the party<u+2019>s story in the obama era has been one of gathering anger within a conservative base increasingly dominated by working-class whites. that anger won republicans control of congress, but also led to the ouster of a house speaker, set the rank-and-file against other party leaders and was crucial to the nomination of a presidential candidate who burdens the rest of the ticket. it wasn<u+2019>t always that way, as republican leaders were able to harness that negative energy at first. after mr. obama inherited an economy in crisis, they fanned the tea party rebellion against his stimulus program, his health care plan and bailouts for wall street and the auto industry. less noticed was the fact that mr. trump was building a political profile by questioning the birthplace and thus constitutional legitimacy of the first african-american president. as republicans gained responsibility for governing, the flames turned inward. in 2011, after regaining a majority in the house, they shoved leaders aside and caused a credit downgrade by balking at an increase in the debt limit . then the government was shut down; the house majority leader, eric cantor, was defeated by a tea party challenger in virginia; and the house speaker, john a. boehner, resigned under pressure. after mr. romney<u+2019>s 2012 defeat exposed the limits of relying on white voters in a diversifying nation, the republican national committee called for outreach to latino voters through new immigration policies. hostility from working-class conservatives, irate over cultural change and diminished economic prospects, scuttled that effort. in the 2016 primaries, jeb bush and marco rubio, two champions of latino support, were punished, and the party was left with mr. trump and senator ted cruz, two finalists for the presidential nomination that republican officeholders loathed but could not stop. mr. trump prevailed by channeling republican anger most skillfully <u+2014> against foes inside the party, like mr. cruz, and out. to the chagrin of fellow republicans now facing general election battles, he hasn<u+2019>t stopped. since securing the nomination, mr. trump has openly denigrated a mexican-american federal judge, the muslim parents of a fallen american soldier and a former miss universe. he offers sweeping condemnations of life in african-american communities. political researchers, and some republican intellectuals, have identified a correlation between support for mr. trump and racial resentment of nonwhites. <u+201c>the gravitational center of the republican party is white nationalism,<u+201d> avik roy, an indian-american who has been a policy adviser for mr. romney and mr. rubio, lamented this summer. the rise of mr. trump threatens fellow republicans who must appeal to broader constituencies, now and in the future. prominent voices within the party, including editorial writers at conservative newspapers and top officials in past republican administrations, have strongly denounced him. asked in a debate this week whether mr. trump represented a role model for children, sen. kelly ayotte, republican of new hampshire, answered <u+201c>absolutely.<u+201d> within hours she found that answer such a liability that she withdrew it, explaining <u+201c>i misspoke.<u+201d> mitch mcconnell, the senate republican leader, in theory allied with his party<u+2019>s nominee, tried this week to avoid that pitfall altogether. asked to discuss mr. trump, who currently draws support from more than eight in 10 republicans, mr. mcconnell told reporters, <u+201c>i choose not to.<u+201d> a version of this article appears in print on october 7, 2016, on page a2 of the new york edition with the headline: republicans are battling themselves. order reprints | today's paper | subscribe
donald trump takes advantage of a republican party pitted against itself
john harwood