Washington (CNN) Boosters of Donald Trump's candidate to be the next secretary of state talk about his experience leading one of the world's largest companies -- and so do his detractors.

Fans of ExxonMobil CEO Rex Tillerson say running a global energy company equips the 64-year-old with the management tools needed to represent the US abroad. Skeptics say a closer look at that experience raises questions about conflicts of interest and whether the nominee would put US or corporate interests first.

The criticism is bipartisan, with both Republicans and Democrats voicing reservations about the Texan. Scientists, human rights activists and environmental groups also raised concerns Tuesday at the news of Tillerson's nomination.

What's their problem? They have a few. Here's a look.

The swamp

Trump campaigned hard on the promise that he would "drain the swamp" and target "global special interests" that partner with "corrupt" Washington politicians to rob "our working class."

Yet Tillerson was recommended to the President-elect by three former government heavyweights: former secretaries of state James Baker and Condoleezza Rice and former Defense Secretary Robert Gates. All three, after their government careers, have benefited financially from ExxonMobil contracts.

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Tillerson, while a Washington outsider, would also be the latest millionaire to join Trump's Cabinet, which already has at least seven millionaires and two billionaires. And ExxonMobil, critics say, is the embodiment of global corporate power, a private empire with its own foreign policy.

"People did not vote on November 8 to ... have the international corporate establishment be the face of America's workers and interests around the world," said Stephanie Taylor, co-founder of the Progressive Change Campaign Committee.

The Trump transition team did not respond to a request for comment.

Russia

This will likely be the biggest hurdle to clear in confirmation hearings. Tillerson has spearheaded ExxonMobil partnerships with a Russian energy company with ties to President Vladimir Putin, who has given him Russia's highest honor for a non-citizen.

That connection has fueled concerns particularly because of Russia's alleged hacking of the elections and Trump's conciliatory stance toward Moscow, which many lawmakers see as a geopolitical threat. They point to Russian support for the Syrian regime, its 2014 annexation of Crimea, its destabilizing actions in eastern Ukraine and aggressive moves against NATO allies.

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Trump has rejected the intelligence community assessment that Russia was behind the hacks and has appointed a national security adviser who, at one point, was paid for appearances on a state-backed Russian TV network. That makes Tillerson's closeness to Putin additionally worrying for Russia critics.

Florida Republican Sen. Marco Rubio said on Twitter Sunday that "being a 'friend of Vladimir' is not an attribute I am hoping for from a #SecretaryofState." Republican Sen. Chuck Grassley of Iowa tweeted Tuesday that "both Trump and Tillerson need to know that Putin is Machiavellian."

Democrats share the concern. Tillerson's status as "a pal of Russia's authoritarian leader" sends a very troubling message to the international community, said Democratic presidential primary challenger and Vermont Sen. Bernie Sanders.

New Jersey Democratic Sen. Robert Menendez went a step farther, charging that Tillerson's appointment would mean that "Dictator Vladimir Putin has a willing accomplice in the Presidential Cabinet guiding our nation's foreign policy."

To be sure ...

ExxonMobil has worked with the State Department on international projects and several career diplomats said the CEO's wealth of international experience could be a welcome change in US diplomacy.

Others pointed out that some of Tillerson's positions might balance out Trump opinions that aren't popular at State. ExxonMobil has begun to support the Paris climate agreement and some diplomats said Tillerson's support might sway Trump, who is a skeptic.

Tillerson has also spoken about the possibility of doing business with Iran, which would support the nuclear deal with Tehran. But there are other grounds for concern, Tillerson's critics say.

Sanctions

Lawmakers are wary of Tillerson's opposition to sanctions against Russia, imposed for its annexation of Crimea. In regulatory filings, ExxonMobil said it stood to lose up to $1 billion because of sanctions on Russia. And it would likely gain if those sanctions were lifted.

Sanctions punish states that break international norms or threaten others, and advocates say that failing to impose them allows countries to break international rules without consequence.

"It troubles me gravely that Mr. Tillerson would have reason to advocate for the rolling back of sanctions because that would be the best interests of his company," said Delaware Democratic Senator Chris Coons. "It is my hope that he is enough of a patriot to be able to separate his decades-long affiliation with this major oil company and the genuine interest of the American people."

Human rights

ExxonMobil has a stated policy of promoting human rights, but under Tillerson it has nevertheless worked in close partnership with repressive regimes, critics say.

Promoting human rights has been a pillar of US foreign policy, as -- beyond any moral imperative -- repression often leads to rebellion, which can destabilize countries, regions and trade. While US administrations can have no choice but to deal with repressive regimes, they usually emphasize the need to honor human rights in private diplomatic exchanges, if not publicly.

"Tillerson oversaw lucrative business operations in partnership with abusive and corrupt oil-rich governments such as Equitorial Guinea and Angola," said Sarah Margon, Washington director for Human Rights Watch. Under Tillerson, the company has opposed US laws requiring stronger human rights standards and greater financial transparency in such countries, HRW said.

Exxon Mobile spokesman Alan Jeffers said the company's human rights policy is consistent with UN guidelines and adds that "we are a longstanding, leading supporter of transparency initiatives."

Climate change

And then there's ExxonMobil's track record on climate change. While the company has come out in support of the Paris climate agreement, environmental groups have charged that the corporation for decades covered up knowledge of the link between fossil fuels and climate change, funded climate denial and caused man-made catastrophes like the Exxon Valdez oil spill in Alaska in 1989.

The US military considers climate change an element of national security because it can intensify security challenges. As secretary of state, Tillerson would represent the US in international climate talks, such as the 2015 Paris agreement signed by 200 nations.

Tillerson has "disparaged and downplayed the science on climate change, and his company is even currently under investigation for defrauding the public and shareholders for decades about the dangers of climate change caused by fossil fuels," said Ken Kimmel, president of the Union of Concerned Scientists.

Jeffers denied the charges, saying that environmental groups had consistently and deliberately mischaracterized the company's track record.

"It's part of a campaign these groups have been running for years to misrepresent our position on climate change," Jeffers said. "The risk of climate change is real."

Light resume on diplomacy

Concern about Tillerson's views on sanctions, human rights and climate change feed into broader questions about whether his lifetime career at Exxon Mobil and the corporate focus on profit are the best preparation for being the top US diplomat.

"The fact is, the art of diplomacy entails much more than the ability to strike a good deal," said Menendez. "Striking a business deal where profits are the only end goal is fundamentally different than being tasked with forging lasting peace accords across the world, protecting America's national security and interests, and defining our response and role to an international crisis."

Connecticut Sen. Chris Murphy, a Democrat, said it was a question of priorities.

"There is no doubt Rex Tillerson is a successful businessman and a very smart person," Murphy said, "but he has proven, many times, his willingness to put oil profits before national interests and handing him the keys of US foreign policy is a recipe for disaster."