WASHINGTON (AP) ― Jon Huntsman, the former ambassador to China who tried to avoid partisan attacks during a presidential campaign that never connected with Republican primary voters, will withdraw Monday from the race for the nomination, campaign officials told the Associated Press on Sunday.

Huntsman will endorse front-runner Mitt Romney at an event in South Carolina, where the next primary will be held, the officials said. Huntsman believes Romney is the best candidate to beat President Barack Obama in November, they said.

The campaign officials spoke on condition of anonymity because Huntsman plans to make the official announcement Monday.

The former Utah governor placed third in last week’s New Hampshire primary despite devoting most of his campaign resources to the state. He had already acknowledged that expectations for him in South Carolina’s primary this week will be “very low.”

Word of the Huntsman withdrawal came on the same day The State, South Carolina’s largest newspaper, endorsed him for president.

The endorsement said there were “two sensible, experienced grown-ups in the race,” referring to Romney and Huntsman. But it said Huntsman “is more principled, has a far more impressive resume and offers a significantly more important message.”

Huntsman’s resume suggested he could be a major contender for the Republican nomination: businessman, diplomat, governor, veteran of four presidential administrations, an expert on China and on foreign trade. With a personal fortune based on his family’s global chemical company, he could be a late entry into the nomination contest without necessarily hobbling his campaign.

Yet Huntsman was almost invisible in a race often dominated by Romney, a fellow Mormon.

To distinguish his candidacy in a crowded field, Huntsman positioned himself as a tax-cutting, budget-balancing chief executive and former business executive who could rise above partisan politics. That would prove to be a hard sell to the conservatives dominating the early voting contests, especially in an election cycle marked by bitter divisions between Republicans and Democrats and a boiling antipathy for President Barack Obama.

Huntsman also tried to offer a different tenor, promising a campaign marked by civility. “I don’t think you need to run down somebody’s reputation in order to run for the office of president,” he said.

While Huntsman was often critical of his former boss ― he joined those saying Obama had failed as a leader ― and occasionally jabbed at Romney, he spent more of his time in debates pushing his own views for improving the economy than thumping the president or his opponents.

In light of his work in the Obama administration, Republicans seemed wary of Huntsman. While he cast his appointment in August 2009 as U.S. ambassador to China as answering the call to serve his country, his critics grumbled that he had in fact been working on behalf of the opposition.

Huntsman was conservative in matters of taxes and the reach of the federal government, but he was out of step with most conservatives in his support of civil unions for gay couples. On matters of science, he poked fun at his skeptical rivals in a pre-debate tweet: “To be clear. I believe in evolution and trust scientists on global warming. Call me crazy.”

In the end, Huntsman didn’t seem to register, crazy or otherwise, with Republicans looking for an alternative to Romney or a winner against Obama. Huntsman was routinely at the bottom of national polls, barely registering at 1 or 2 percent, a reflection of the faint impression he made in the Republican debates.