First Read is your briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Tweeting and fuming, Trump spirals further into crisis

For a presidency that’s already in crisis — see his 36 percent job-approval rating per Gallup or this Thursday’s upcoming testimony by former FBI Director James Comey — the last 24 hours or so have been extraordinarily horrendous for President Trump.

For starters, there was his out-of-context shot at London’s mayor after the terrorist attack on the city Saturday night (before playing a round of golf). Then there were his tweets this morning that called his revised travel ban “watered down” and “politically correct,” potentially undermining his administration’s legal defense that the ban doesn’t discriminate against Muslims. And then there’s this stunning Politico article — that Trump deliberately failed to include language in his recent NATO speech reaffirming the alliance’s Article 5 provision.

National Security Adviser H.R. McMaster, Defense Secretary Jim Mattis and Secretary of State Rex Tillerson all supported Trump doing so and had worked in the weeks leading up to the trip to make sure it was included in the speech, according to five sources familiar with the episode. They thought it was, and a White House aide even told the New York Times the day before the line was definitely included.It was not until the next day, Thursday, May 25, when Trump started talking at an opening ceremony for NATO’s new Brussels headquarters, that the president’s national security team realized their boss had made a decision with major consequences – without consulting or even informing them in advance of the change.

Four and a half months into Trump’s presidency, it’s easy for political observers to become numb to every controversy and crisis coming from the White House. But this bears emphasizing: This is a president who, day after day, is destroying his credibility.

The Alarmist-in-Chief

Staying with Trump’s attack on London’s mayor and his travel-ban tweets, here’s the Washington Post’s Phil Rucker: “A traditional president would have reacted carefully to the London Bridge terrorist attack by instilling calm, being judicious about facts and appealing to the country’s better angels. But Donald Trump is no traditional president. He reacted impulsively to Saturday night’s carnage by stoking panic and fear, being indiscreet with details of the event and capitalizing on it to advocate for one of his more polarizing policies and to advance a personal feud… Later that evening, Trump spoke with British Prime Minister Theresa May and extended his support for America’s closest ally. He tweeted, ‘Whatever the United States can do to help out in London and the U. K., we will be there — WE ARE WITH YOU. GOD BLESS!’ On Sunday morning, however, once the breadth of the horror in London was clear, Trump was back on Twitter. He criticized the city’s mayor — Sadiq Khan, a liberal Muslim and an old Trump foil — for not being tough enough protecting his citizens.”

It isn’t every day when Ariana Grande displays more compassion and inspiration than the president of the United States, but here we are.

Previewing Comey’s big testimony on Thursday

Former FBI Director James Comey’s testimony Thursday to the Senate Intelligence Committee promises to be one of the most highly anticipated congressional appearances in years. Indeed, for a comparable high-stakes hearing, you have to go back to 2015, when Hillary Clinton testified before the House Benghazi Committee. Or 1991, when Anita Hill testified in Clarence Thomas’ Supreme Court confirmation hearing. Or 1987, when Oliver North testified on the Iran-Contra scandal. So Thursday is THAT big. And there will be four storylines to watch:

Why does Comey think President Trump fired him? Did it have anything to do with the Russia investigation and a possible obstruction of justice? Does Comey confirm that Trump asked him to let go of the probe into former National Security Adviser Michael Flynn? Does Comey confirm that Trump asked him to pledge his loyalty to the president? And do Trump and his administration try to stop Comey’s testimony by invoking executive privilege? On Friday, the New York Times, citing two senior administration officials, reported that Trump doesn’t plan to prevent Comey’s testimony.

And keep in mind: Comey knows how to tell a story, as the Washington Post’s Paul Kane recounted several years ago about the former FBI director’s congressional testimony into his intervention when Bush Attorney General John Ashcroft was hospitalized. “… Comey wanted to tell this amazing story about a constitutional crisis in the hospital room of then-Attorney General John Ashcroft in 2004. So [former Chuck Schumer staffer Preet] Bharara arranged for Comey to testify before a Senate subcommittee. The usually loquacious Schumer stopped asking Comey questions and just let him give a long statement telling the tale of something that seemed like a movie plot. You could hear a pin drop in the Dirksen hearing room, and in fact we did, when one reporter — stunned at what he was hearing — literally just dropped his pen onto the press table.”

Political crisis in the Persian Gulf

So much for the one part of Trump’s overseas trip that looked it like it was a success. The AP: “Four Arab nations cut diplomatic ties to Qatar early Monday morning, further deepening a rift among Gulf Arab nations over that country's support for Islamist groups and its relations with Iran. Bahrain, Egypt, Saudi Arabia and the United Arab Emirates all announced they would withdraw their diplomatic staff from Qatar, a gas-rich nation that will host the 2022 FIFA World Cup and is home to a major U.S. military base. Saudi Arabia also said Qatari troops would be pulled from the ongoing war in Yemen.”

Megyn Kelly interviews Putin

NBC News on Megyn Kelly’s interview with Russian President Vladimir Putin: “Kelly met Putin in St. Petersburg, the Russian president's hometown and his nation's onetime capital, after sharing a contentious discussion about Russia's attempts to hack the 2016 election at the St. Petersburg World International Economic Forum. Putin, a former KGB agent, has been painted as the puppet master behind the challenge on November's voting. U.S. intelligence agencies have concluded that Putin ordered the disruption of the election. During the interview, Putin tried to dismiss the evidence by claiming that the United States has a history of meddling in foreign elections. ‘Put your finger anywhere on a map of the world, and everywhere you will hear complaints that American officials are interfering in internal electoral processes,’ he said. Kelly pushed back at the assertion, saying it sounded like Putin's attempt to justify his government's attempts to influence elections. Putin demurred.”

It’s Infrastructure Week for the Trump White House

“President Trump will lay out a vision this coming week for sharply curtailing the federal government’s funding of the nation’s infrastructure and calling upon states, cities and corporations to shoulder most of the cost of rebuilding roads, bridges, railways and waterways,” the New York Times writes. “He will also endorse a plan to privatize and modernize the nation’s air-traffic control system. That plan, which is to be introduced on Monday at the White House and the subject of a major speech in the Midwest two days later, will be Mr. Trump’s first concrete explanation of how he intends to fulfill a campaign promise to lead $1 trillion in United States infrastructure projects. The goal is to create millions of jobs while doing much-needed reconstruction and updating. But the actual details of the initiative are unsettled, and a more intricate blueprint is still weeks or even months from completion.” But to get infrastructure passed through Congress, Trump will need Democratic votes. And here’s the current reaction from that side of the aisle: “POTUS is NOT proposing money for infrastructure. It's tax cuts for financiers, privatizing public property. Not infrastructure,” Sen. Brian Schatz (D-HI) tweeted.