Donald Trump, faced with opposition inside and outside his party, plans to renew the nationalist themes that built his base and amplify his no-holds-barred attacks against Hillary Clinton to depress Democratic voter turnout, his advisers said.

Following the release of a tape-recording of his lewd comments about women and several high-profile Republican defections over the weekend, Mr. Trump has effectively given up the conventional wisdom of trying to reach voters far outside his core of support, one high-level Republican supporter said…

Ryan Williams, a Republican strategist who was an aide on Mitt Romney’s two presidential campaigns, said the strategy of attacking other Republicans showed a “complete lack of focus” at a time when the Trump camp should be “trying to shift the focus back to Hillary Clinton and her record.”

Kevin Madden, a Republican strategist who worked on the presidential campaigns of Mr. Romney and George W. Bush, said Mr. Trump’s approach would drive turnout among his base, “but alienating his own party and swing voters won’t grow his vote. His remarks and tactics can have the adverse effect of energizing the Democratic base.”