John Bolton, a leading candidate to be second-in-command at the State Department, is encountering headwinds -- including from Trump's choice to lead the agency -- a source familiar with transition talks said.
Rex Tillerson, the ExxonMobile CEO tapped to become the country's top diplomat, has expressed reservations about Bolton, the source said.
Bolton, who served under President George W. Bush as both an undersecretary of state and ambassador to the UN, is also drawing objections from some former top Republican officials.
Former Secretaries of State Condoleezza Rice and James Baker, along with Stephen Hadley, a former national security adviser to Bush -- all of whom lobbied for Tillerson -- have misgivings about Bolton, according to a source familiar with the deliberations over Bolton's candidacy.
But the brusque and opinionated Bolton is as loved in some quarters for his uncompromising conservativism as he is loathed in others -- particularly among diplomats -- for his views and style.
Bolton and the transition team haven't responded to several requests for comment. The friction over Bolton, just the latest public mini-drama as Trump builds his administration, reflects rifts within the Republican national security establishment dating back to the Iraq War -- a group already deeply divided over Trump himself.
The deputy position requires Senate confirmation and there are already indications it would be an uphill battle for Bolton. The nine Democrats on the committee are unlikely to support him.
Delaware Democratic Sen. Chris Coons, another member of the Foreign Relations Committee, told CNN that Bolton is an "unreconstructed neocon who still believes the Iraq War was a great idea, despite all the evidence to the contrary."
Coons added that in combination with Tillerson, Bolton would "provide little restraint on the President-elect and a national security team that strikes me as too heavily inclined towards the use of force rather than diplomacy."
And Kentucky Republican Sen. Rand Paul, also a committee member, has made clear he opposes Bolton because of the former diplomat's support for the Iraq War.
Bolton, 68, has told supporters and friends he doesn't want the deputy job -- and his foreign policy views in many ways clash with Trump's -- but he has spent the past several days in New York available to the Trump team.
His supporters have told him to accept the post if it's offered, in part because Tillerson's lack of experience with the State Department means Bolton would have tremendous power to shape the agency.
Moreover, these supporters add, there are doubts that Tillerson would be interested in staying for the entire four-year term, which could pave the way for Bolton to step into the top job.
But much of Bolton's world view is at odds with the foreign policy campaign pledges laid out by Trump.
Bolton has been highly critical of Russia, while Trump has repeatedly stressed the need for greater cooperation with Moscow.
Trump, who initially backed the Iraq War, has strenuously touted his later opposition to it. Bolton backed the Iraq War and supports regime change through military action in certain cases.
As the State Department's No. 2, the key management position, Bolton could be in a position to quash diplomatic and bureaucratic efforts to push Trump's agenda.
Indeed, while serving under former Secretary of State Colin Powell, Bolton was criticized by the secretary's aides for leaking to reporters to undermine aspects of Powell's policies that he didn't agree with. Among his fellow diplomats, he was seen by some as too extreme and hostile to international law and institutions.
"Bolton seems to spend more time and energy criticizing the individuals and institutions protecting human rights, rather than the human rights violators themselves," said Sarah Margon, Washington director of Human Rights Watch.
Others, though, praised Bolton as a talented diplomat who succeeded at getting other countries to cooperate with the Bush administration's agenda.
Sen. Lindsey Graham, a South Carolina Republican who also sits on the Foreign Relations Committee, praised Bolton as "a reformer who would turn the State Department upside down and make it work better. He understands who our friends and enemies are."
Robert O'Brien, a California-based attorney who worked for Bolton at the United Nations, praised him as "a formidable diplomat."
O'Brien continued, "Everyone who did so walked away a better diplomat because of the experience. He is a very skilled ambassador."
In some respects, Bolton could fit easily onto a national security team fashioned around Trump's "America First" foreign policy. Like Trump, Bolton has been exceedingly critical of the Iran nuclear deal. And like the President-elect, Bolton is skeptical of international institutions and treaties that he claims threaten US interests or sovereignty.
While serving under Bush, Bolton worked to removed America's signature from the treaty creating the International Criminal Court, and negotiated over 100 bilateral agreements to prevent Americans from being delivered into the ICC's custody. He also negotiated the US withdrawal from the 1972 ABM Treaty, paving the way for George W. Bush to develop a missile-defense program.
Trump is considering others for the deputy job, transition sources said, including former State Department official Richard Haass, president of the Council on Foreign Relations.
Haass spoke to Trump last week by phone and met with the transition team at Trump Tower on a "wide range of issues and personalities," according to a source who said the team was asking for his advice on policy and staffing choices.
At no time was the deputy job raised with Haas, the source said.