President Trump has been pressuring Senate Republicans to trash the filibuster and pass a bill disenfranchising millions of voters and boosting their party’s chances of controlling Congress after next fall’s elections. But Sen. John Thune, the Republican leader, keeps telling Trump that the votes are simply not there.

“My job, obviously, is to define reality, and the reality is that it’s not even a close call,” he told Punchbowl News. “A large number of Senate Republicans … feel very strongly about the filibuster, its role in our democracy, and the role it plays in giving a voice to the minority.”

Trump’s tantrums are often far removed from reality, and the president is such a persistent and powerful prevaricator that Republicans generally play along, fearing his wrath and fervidly fostering his fantasies. So, it’s particularly important that leaders like Thune take on the totally thankless task of telling Trump the truth.

Another courageous voice in Republican ranks is Sen. Rand Paul of Kentucky, a true conservative who actually believes a president should keep the promises he made to voters. And Trump, he keeps insisting, vowed to end wars, not start them.

“America is at war,” Paul has posted on social media. “But Americans don’t want this war. They didn’t vote for it. In fact, they voted for just the opposite.”

Moreover, he insists, the Constitution gives Congress, not the president, the power to make war. “No others in our history have been this cavalier with our military men and women and tax dollars as they are at this moment,” writes the senator. “I urge my colleagues to join me in opposing both this war and the unilateral actions taken without congressional authorization, as the Constitution commands.”

The Constitution serves as a critical bulwark against Trump’s raid on reality. This tension was on full display at the Supreme Court recently, when Trump’ solicitor general, D. John Sauer, argued that “birthright citizenship” should be revised in light of easy international travel that makes “birth tourism” possible.

“It’s a new world,” Sauer argued.

“It’s a new world,” retorted Chief Justice John Roberts. “It’s the same Constitution.”

That “same Constitution” also thwarted Attorney General Pam Bondi, who was repeatedly pressured to bring criminal cases against Trump’s enemies, such as former FBI director James Comey and New York Attorney General Letitia James. “They’re all guilty as hell, but nothing is going to be done,” the president fulminated last fall.

As a besotted courtier, Bondi tried to please the monarch, but the cases she brought were so flimsy they kept falling apart. And Bondi finally fell, too — fired by an irate Trump because she couldn’t bend the rule of law to his liking.

All federal judges are appointed for life, and that gives them a vital immunity from presidential efforts to pervert the legal system. Trump could not contain his anger when six justices — including two he had appointed, Neil Gorsuch and Amy Coney Barrett — voted against his scheme to bypass Congress and impose tariffs by executive order.

He called the justices “unpatriotic and disloyal to our Constitution” when, in fact, they were exactly the opposite: loyal patriots who resisted the president’s assault on enduring constitutional principles.

The economy is another crucial area where Trump remains defiantly detached from immutable evidence. In his recent televised speech, he asserted, “We were a dead and crippled country after the last administration and made it the hottest country anywhere in the world by far, with no inflation.”

That is simply false. Inflation is running at 2.4% annually. Plus, the Iran war has already driven gas prices to a national average well past $4 a gallon, and despite the two-week ceasefire, the wider impact of that increase will continue to filter through the rest of the economy. Amazon, for instance, has announced a surcharge on all deliveries because of rising fuel costs, and as the Washington Post put it, “Even if the conflict resolves in the next few weeks, some economic pain will linger for months.”

Jamie Dimon, the longtime CEO of JP Morgan Chase, who is known for his clear-eyed devotion to economic reality, rebutted Trump’s rosy vision in his annual letter to his shareholders: “Now, because of the war in Iran, we additionally face the potential for significant ongoing oil and commodity price shocks, along with the reshaping of global supply chains, which may lead to stickier inflation and ultimately higher interest rates than markets currently expect,” Dimon wrote.

Reality always rules. The Constitution remains. That’s why the voices devoted to facts, not fantasies, are so valuable.