Thanksgiving is my favorite holiday. It’s a secular celebration of America, and as an immigrant, I feel I have much to be grateful for. I am an optimist who tends to see the story of this country as one of addressing its shortcomings and making progress. Lately, it has been tough to maintain that sunny outlook. America’s greatest assets — its constitutional republic and its democratic character — seem to be in danger of breakdown.

Listen to the language of the president. “Our radical Democrat opponents are driven by hatred, prejudice and rage,” he thundered at a June rally to kick off his reelection campaign. “They want to destroy you, and they want to destroy our country as we know it.” Words such as “treason” and “coup” are now casually tossed around in political discourse. Some had imagined that the impeachment inquiry might provide evidence and facts that would cut through the spin and fantasies, but in fact the opposite has happened. It’s clear now that the intensity of polarization is so great that everything is viewed through a partisan prism. Can America survive through such poisonous times?

Well, it has in the past. The American republic is an extraordinary creation, built to accommodate very different people with utterly different ideas and values. It has survived the battles between slave owners and abolitionists, the First Red Scare and McCarthyism, Vietnam and Watergate. All of those struggles were high-stakes affairs, each aroused passions, and each eventually ended, though not without bitterness and disappointment. History, even the history of a powerful and successful country such as the United States, is not a collection of merry tales with happy endings. It’s full of fights, with wins, losses and draws.

Could this time be different? Yes, says Yoni Appelbaum in a thought-provoking essay in the Atlantic titled “How America Ends.” Appelbaum argues that “the United States is undergoing a transition perhaps no rich and stable democracy has ever experienced: Its historically dominant group is on its way to becoming a political minority — and its minority groups are asserting their co-equal rights and interests.” Ezra Klein notes a related transformation: “Almost 70% of American seniors are white and Christian. Only 29% of young adults are white and Christian.”

Appelbaum acknowledges that there have been smaller versions of this transition before, but those moments have been wrenching, often stretching America to the breaking point. It took a civil war to end slavery and then almost 100 years of struggle to end Jim Crow. The United States passed the Chinese Exclusion Act and interned 120,000 U.S. citizens and noncitizens of Japanese descent before opening its gates to immigrants from all over the world. Women had to wage a long campaign to secure the right to vote, and gays had to overcome systematic discrimination and persecution before gaining acceptance. Today, the country is locked in a new battle over sweeping demographic shifts.

There is another concerning trend that threatens America’s constitutional character: the ever-expanding power of the presidency. Whatever you think of the charges against President Trump on Russia or Ukraine, his position of resolute noncooperation with Congress should trouble you deeply. If Congress cannot exercise its core oversight capacity, obtain documents and subpoena administration officials to testify, the essential system of checks and balances has broken down. The presidency will have become an elected dictatorship.

We have been going down this road for a while. Arthur M. Schlesinger Jr. wrote about “The Imperial Presidency” in 1973. The legislation and culture after Watergate led many to believe that matters were under control. People actually began worrying about a weakened and emasculated White House. In fact, as Schlesinger noted in a 2004 reissue of his book, the presidency in recent years has become stronger than ever. The fear after 9/11 proved to be the gateway for an out-of-control executive branch. The president gained the ability to snoop on private Americans, use military force at his whim, torture prisoners and detain people indefinitely. The president can now order the execution of American citizens who are deemed — by him — to be terrorists, without due process.

In Attorney General William P. Barr, Trump has found an extraordinarily useful aide, who appears to believe, despite all this history, that the great problem in the United States is that the presidency is too weak. He has enabled a policy of stonewalling and silence, in which top administration officials almost behave as though Congress does not exist. People often ask themselves what the founders would think of America today. It seems to me that the greatest shock to them would be the incredible growth of presidential power. Congress and the courts are recognizable from their times; the White House is not.

Tensions over profound demographic change, fierce political backlash and a presidency that refuses to be checked. My optimism is wearing thin.