At a packed community center in southwestern Iowa, Nikki Haley broke from her usual remarks this month to offer a warning to her top Republican presidential rivals, Donald J. Trump and Ron DeSantis, deploying a favorite line:
“If they punch me, I punch back — and I punch back harder.”
But in that Dec. 18 appearance and over the next few days, Ms. Haley, the former governor of South Carolina, did not exactly pummel her opponents as promised. Her jabs were instead surgical, dry and policy-driven.
“He went into D.C. saying that he was going to stop the spending and instead, he voted to raise the debt limit,” Ms. Haley said of Mr. DeSantis, a former congressman, in Treynor, near the Nebraska border. At that same stop, she also defended herself against his attack ads and criticized Mr. DeSantis, the Florida governor, over offshore drilling and fracking, and questioned his choice of a political surrogate in Iowa.
She was even more careful about going after Mr. Trump, continuing to draw only indirect contrasts and noting pointedly that his allied super PAC had begun running anti-Haley ads.
“He said two days ago I wasn’t surging,” she said, but now had “attack ads going up against me.”
With under three weeks left until the Iowa caucuses, Ms. Haley is treading cautiously as she enters the crucial final stretch of her campaign to shake the Republican Party loose from the clutches of Mr. Trump. Even as the former president maintains a vast lead in polls, Ms. Haley has insistently played it safe, betting that an approach that has left her as the only non-Trump candidate with any sort of momentum can eventually prevail as primary season unfolds.
On the trail, she rarely takes questions from reporters. She hardly deviates from her stump speech or generates headlines. And she keeps walking a fine line on her greatest obstacle to the Republican nomination — Mr. Trump.
“Anti-Trumpers don’t think I hate him enough,” she told reporters this month in New Hampshire, where she picked up the endorsement of Chris Sununu, the state’s popular Republican governor. “Pro-Trumpers don’t think I love him enough.”
Ms. Haley’s consistent strategy has enabled her team to build a reputation as lean and stable where other campaigns have faltered: As Mr. DeSantis’s support has dipped and turmoil has overtaken his allied super PAC, even some of his advisers are privately signaling they believe hope is lost.
“I keep coming back to the word ‘disciplined,’” said Jim Merrill, a Republican strategist in New Hampshire who served on Senator Marco Rubio’s 2016 presidential campaign and Mitt Romney’s 2008 and 2012 bids. “She has run an extraordinarily disciplined campaign.”
Yet Mr. Trump remains the heavy favorite for the nomination despite facing dozens of criminal charges, as well as legal challenges that aim to kick him off the ballot in several states.
Ms. Haley’s apparent reluctance to attack her rival even in the face of what would seem to be political setbacks for him has raised questions from voters and other Republican competitors — most notably, former Gov. Chris Christie of New Jersey — about whether she can win while passing up crucial opportunities to derail her most significant opponent.
