Congressional Republicans said Tuesday that Donald Trump’s nomination of Rex Tillerson to run the State Department gave them “serious concern,” raised “red flags,” and prompted “many questions which must be answered.” 

But as the Senate GOP considers blocking the Exxon Mobil CEO, it should ask itself: Can it risk open conflict with Trump?

Defying the president-elect’s wishes could elicit a harsh rebuke from Trump, who, in the past, has relished castigating fellow Republicans who disagreed with him. And the resulting split could put congressional Republicans — whether individually or as a group — on the wrong side of Trump’s die-hard legion of supporters, who could either rebel in a primary or hold back support in the general election.

Many of those supporters were key to the GOP’s unexpectedly strong showing down ballot last month, victories that were thanks, in part, to Trump’s surprising showing.

Such a conflict might not begin over Tillerson. Senate Majority Leader Mitch McConnell, in fact, issued a statement Tuesday saying that he “looks forward to supporting his nomination,” an indication that most members of his conference will back Trump’s pick.

Inevitable clashes

But Republican political operatives worry that congressional Republicans and Trump will inevitably clash on issues such as infrastructure spending, adjustments to the social safety net, or immigration, on which the two sides have already signaled some disagreement.   

“Both Trump and Tillerson need to know that Putin is Machiavellian and gets rid of [people] who expose him as such,” Sen. Charles E. Grassley of Iowa tweeted Tuesday morning. “Both Bush & Obama were [hoodwinked].”

A confirmation fight over the secretary of State might just be a preview of what’s to come. Republicans will argue that providing a check on Trump’s decisions is exactly what many of them promised to do during their own campaigns and that retaining independence from the volatile leader is in the party’s short- and long-term political interests.

But just in the last campaign, top Republican strategists (in a conclusion even most Democrats privately agreed with) came to believe that supporting Trump was more politically beneficial for Republicans running in competitive races than opposing him, given the severe backlash many Republican candidates faced if they didn’t.

Opposing Trump’s pick for secretary of State is not tantamount to opposing his presidency, but in the eyes of some Trump supporters, it might be close.

Some Republicans are concerned about Tillerson because of his, in the CEO’s own words, “very close relationship” with Russian President Vladimir Putin. As Exxon Mobil’s CEO, Tillerson has negotiated oil agreements with Putin and in 2013, he received the Russian Order of Friendship award.

Sen. Marco Rubio of Florida said he had “serious concerns” about Tillerson’s nomination.

“The next secretary of State must be someone who views the world with moral clarity, is free of potential conflicts of interest, has a clear sense of America’s interests, and will be a forceful advocate for America’s foreign policy goals to the president, within the administration, and on the world stage,” Rubio said in a statement. “I look forward to learning more about his record and his views.‎”

‘Front and center’

Sen. Lindsey Graham of South Carolina said he expects “the U.S.-Russian relationship to be front and center in his confirmation process.”

“Based upon his extensive business dealings with the Putin government and his previous opposition of efforts to impose sanctions on the Russian government, there are many questions which must be answered,” Graham said.   

Not every Republican senator expressed those concerns on Tuesday, however, including some lawmakers whose political situation is different than Graham’s or Rubio’s. 

Sen. Jeff Flake of Arizona, for instance, signaled Tuesday he was open to the Tillerson nomination.

“The fact that Condi Rice, James Baker and Bob Gates are recommending Tillerson carries considerable weight,” Flake tweeted. “I look forward to the hearings.”

Flake has been a frequent Trump critic, regularly blasting the GOP leader for his conduct during the campaign. Trump, in turn, has returned fire, calling Flake a “very weak and ineffective senator.”

But he faces re-election in 2018, which means running in a Republican primary in a state that backed Trump overwhelmingly in the GOP presidential primary. And he’s already drawn a primary opponent, former state Sen. Kelli Ward, who counts herself as a strong Trump supporter.