Now that former United Nations Ambassador Nikki Haley has firmly overtaken Florida Gov. Ron DeSantis to be Donald Trump's chief rival, the former president has been ramping up his attacks against her.

This is a contrast from last year when Trump was mostly happy to ignore Haley — and, according to a new report from Rolling Stone, this was part of a deliberate strategy.

Essentially, the Trump campaign wanted to keep Haley in the race and have her battle it out for second place with Florida Gov. Ron DeSantis, whom Trump insiders believed was the one true threat to Trump reclaiming the nomination, the report said.

"Team Trump smartly used Nikki Haley as a weapon of mass destruction to destroy DeSantis’ coalition, knowing that in the end Haley would never be able to put together a winning coalition in the primary, given all the weaknesses she has on the right," explained one source who was described as "close to the campaign."

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But with DeSantis close to being dispatched, the publication's sources say, Trump is gearing up for a full assault on Haley.

"Trump and his reelection operations are now in full-blown 'wreck-Nikki-Haley mode,' one adviser to the ex-president says, and they’re pouring millions into ads and other efforts to bury her," writes Rolling Stone.

While polls have shown Trump comfortably ahead in Iowa, they've also shown Haley making a major surge in New Hampshire, where she's hoping to pull an upset in that state's primary.