With five days left until the New Hampshire primary, Donald J. Trump and his allies are stepping up their efforts to muscle Nikki Haley and Ron DeSantis out of the Republican presidential race by casting Mr. Trump’s nomination as inevitable.

The strategy reflects an urgent desire to end the race quickly and avoid an extended and expensive battle for delegates heading into Super Tuesday on March 5.

Mr. Trump is facing 91 criminal charges in four jurisdictions, as well as two costly civil trials, where he has used voluntary appearances at New York courthouses this month as public relations and fund-raising vehicles. But February offers him few such opportunities, meaning he would need to rely on his political strength alone to generate momentum for Super Tuesday, when voters in 16 states and territories will cast ballots for the nomination.

In New Hampshire, Mr. Trump began attacking Ms. Haley with paid advertising weeks ago, and intensified the onslaught more recently with sharper personal criticisms and campaign statements portraying her as a China-loving globalist. On Tuesday, he went after Ms. Haley, the daughter of immigrants from India, on his social media website, using her birth name — Nimarata, which he misspelled as “Nimrada” — as a dog whistle, much like his exaggerated enunciation of former President Barack Obama’s middle name, “Hussein.”