Tom Cotton, the Republican senator from Arkansas, is becoming President Trump’s right arm in the Senate. Or maybe it’s the other way around, and Cotton, a right-wing ideologue, is helping to steer the president. Either way, Trump’s behavior in the immigration debate—turning against a legislative compromise after Cotton was summoned to a White House meeting to oppose it—illustrates the young senator’s influence. In fact, Trump is said to be considering him as the next CIA director.

Cotton’s emergence is alarming. In part, that’s because what endears Cotton to Trump—and makes them particularly dangerous together—is Cotton’s unflinching willingness, in pursuit of an agenda, to say things that aren’t true.

Cotton is a veteran. He served with honor in Iraq and Afghanistan. But when he came home, he brought back the psychology of war. He treats liberals and moderates as the enemy. In 2015, he blocked one of President Obama’s ambassadorial nominees over an unrelated issue—she eventually died waiting for approval—because Cotton knew she was Obama’s friend. He depicts Obama as a traitor. Last month, Cotton said of the Iran nuclear agreement: “Barack Obama was willing to give away anything to get that deal.”

On immigration, Cotton takes a hard line, and he savages anyone who doesn’t. He calls senators who seek an immigration compromise “the Gang of Amnesty.” He labels their ideas “preposterous” and “utterly ridiculous.” Last week, he scoffed that fellow Republican Sen. Lindsey Graham, an immigration moderate, “didn’t even make it off the kiddie table in the debates” during the 2016 Republican presidential primaries. On Tuesday, after the government shutdown, Cotton crowed that Democrats had “capitulated entirely.”

Cotton is quick to charge others with lying. Two weeks ago, he accused colleagues of floating a “disingenuous” immigration compromise. He said Democrats had “misrepresent[ed]” immigration talks. On Friday, Cotton accused Graham of conspiring with Democratic Sen. Dick Durbin: “Lindsey Graham and Dick Durbin are not adversaries in negotiating. They are allies strategizing.” That line has been used exactly once before, by an anonymous member of Congress—presumably Cotton—who accused House Speaker Paul Ryan of treachery on the same issue. Tucker Carlson reported the accusation last fall:

As one of their colleagues told us just this morning, when Nancy Pelosi and Paul Ryan sit down to talk immigration, they aren’t opponents negotiating, they are allies strategizing … Earlier this year we had Speaker Ryan on this show and he assured us Congress would be working hard on funding the border wall. That was a lie.

In the war at home, Cotton fights for Trump. Each time he’s faced with a choice between Trump and the truth, Cotton protects Trump. Two months ago on Face the Nation, John Dickerson asked Cotton about unresolved sexual misconduct allegations against the president. Cotton brushed the allegations aside, arguing that “the American people had their say on that” when they elected Trump. Last month, when an AP reporter asked Cotton about collusion between Trump and Russia, Cotton dismissed the question, claiming that Democratic Sen. Dianne Feinstein had “said she’d seen no evidence of collusion.” Actually, what Feinstein had said was, “It’s an open question because there’s no proof yet that it’s happened, and I think that proof will likely come with [Special Counsel] Mueller’s investigation.”

Now Cotton is protecting Trump again. On Jan. 11, during an Oval Office meeting, Trump said he wanted fewer immigrants from “shithole” countries in Africa and Haiti and more from Norway and Asia. The president’s comments were leaked, and Durbin, who had witnessed the exchange, publicly recounted them the next day. Cotton, who had also attended the meeting, went on TV to defend Trump. He portrayed Durbin as a liar, saying Trump had never used the expletive reported by Durbin. Dickerson asked Cotton whether Trump, in the meeting, was in any way “grouping people based on the countries they came from.” Cotton denied it. He insisted that Trump had “reacted strongly against” such thinking and that “what the president said he supports is [to] treat people for who they are,” not “where they’re from.”

Cotton was lying. We know this from other Republicans who were in the meeting. On Jan. 16, DHS Secretary Kirstjen Nielsen testified that Trump had specifically praised Norwegians and had worried aloud about not bringing in enough Europeans. An anonymous White House official told the Washington Post that Trump, in addition, had “suggested that he would be open to more immigrants from Asian countries because he felt that they help the United States economically.” Trump also recapitulated his remarks, complaining in tweets that the U.S. “would be forced to take large numbers of people from high crime countries which are doing badly.” And the Post reported that according to “three White House officials,” Cotton and his fellow immigration hard-liner, Sen. David Perdue, had later “told the White House that they heard ‘shithouse’ rather than ‘shithole,’ allowing them to deny the president’s comments on television.”

Cotton told Dickerson that Durbin’s account couldn’t be trusted, because “Sen. Durbin has a history of misrepresenting what happens in White House meetings.” Cotton alluded to a 2013 incident in which Durbin had misquoted a Republican House leader’s comment at an Obama White House meeting. What Cotton didn’t mention was that Durbin hadn’t attended or claimed to have witnessed the 2013 meeting. In that episode, Durbin had simply relayed a report from White House aides, which turned out to be erroneous. By portraying the 2013 incident as grounds to disbelieve Durbin’s firsthand account of the meeting this month, Cotton was misrepresenting the colleague he accused of misrepresentation.

This weekend, after nine days of deception, Cotton was offered a chance to come clean. He spurned it. On Meet the Press, Chuck Todd asked him: “Did the president use a vulgarity?” Cotton demurred: “I’m not going to get into every word that was or was not said.” Again, he claimed that Trump, in the meeting, had rejected the idea of judging immigrants by “where they come from.” Cotton also denied that Graham had challenged Trump during the exchange: “Lindsey Graham made a case about immigration policy. He didn’t make a case about what the president was saying.” In fact, said Cotton, “As far as I know, Lindsey Graham hasn’t spoken on the record about this.”

Again, Cotton’s claims were flatly untrue. By Jan. 18, Graham had recounted the meeting in interviews with the Charleston Post and Courier, the New York Times, and CNN. In his conversation with the Times, the paper reported, “Mr. Graham said that he responded to Mr. Trump’s complaints about Norwegians not migrating to America.” In the CNN interview, Graham affirmed, “I didn’t like what was said. I spoke up.” In the Post and Courier interview, Graham elaborated:

I tried to make it very clear to the president that when you say “I’m an American,” what does that mean? It doesn’t mean that they’re black or white, rich or poor. It means that you buy into an ideal of self-representation, compassion, tolerance, the ability to practice one’s religion without interference and the acceptance of those who are different. … [W]hen I say merit-based, I don’t mean just Europe.

Graham’s interviews falsified Cotton’s lies about the meeting. So Cotton pretended the interviews hadn’t happened. Or, to be more precise, Cotton insisted that Graham hadn’t spoken “on the record.” With that phrase, Cotton revealed his game. He knew what Graham had said and seen in the Oval Office. Cotton just wanted Graham to keep his recollections off the record, so Cotton could preserve his own fictional account.

Anyway, Cotton argued, what happened in the meeting doesn’t matter. “What matters to the American people,” he told conservative radio host Hugh Hewitt on Jan. 16, “is what our immigration policy will be, not what was or was not said in a private meeting and then leaked selectively and dishonestly.” But a week later, Cotton returned to Hewitt’s show, this time peddling his own leaks. “Some of the Democrats with whom we’ve negotiated,” he told Hewitt, “have expressed privately but explicitly their hopes that the enforcement and security mechanisms of a compromise will be struck down in federal courts … That’s one reason why it’s hard to negotiate in good faith.”

That’s Tom Cotton. He lies about a meeting and then lies about the people who truthfully reported it. He calls them leakers and then leaks against them. He talks about good faith as he schemes and smears. In the Senate, he’s a menace. As CIA director, he could do far worse.