David Axelrod, a senior CNN political commentator and host of " The Axe Files ," was senior adviser to President Barack Obama and chief strategist for the 2008 and 2012 Obama presidential campaigns. The opinions expressed in this commentary are his. View more opinion articles on CNN.

(CNN) As I was leaving a speaking engagement recently at Bradley University, a young man, perhaps 30, stopped me and asked for a moment.

During my remarks, I had talked about the epic battle for the Affordable Care Act and my own financial struggles years earlier as the father of a child with a severe, chronic illness and huge medical expenses.

The young man pulled up close and spoke quietly.

"I wanted to tell you that I have a 5½-year-old with a number of serious issues," he said. "We couldn't have handled it and gotten the care he needed without the ACA. I just wanted to say thank you."

I have had more of these conversations than I can count since the ACA took effect. An older couple in a book signing line in Denver, sharing the story of their grandchild, who had an ordeal similar to my Lauren's, but the protection of the ACA; parents relieved that their adult children could stay on their insurance until the age of 26.

And then there was the American couple who chased me down after an insurance conference I addressed in Calgary. She had a highly advanced cancer that required extensive and expensive therapy. Without the ACA, she said, she would have run up against a lifetime cap on her insurance policy. The law banned such limits. She survived.

"We just wanted to ask you if you could thank President Obama for us," her husband said, hugging his tearful wife tightly.

I thought about these stories this week when I learned of President Trump's decision to change course and join a right-wing push, led by Republican state attorneys general, to invalidate the Affordable Care Act in the courts.

The ACA has meant health coverage for millions of working Americans and their families who otherwise would not have had it. It also bans insurance companies from imposing lifetime caps and refusing coverage to people with pre-existing conditions like my daughter's epilepsy.

Most Americans agree that discriminating against people with chronic conditions or serious illnesses is wrong. One of the major reasons Republicans lost control of the House of Representatives in November was precisely the efforts of President Trump and the GOP to roll back the ACA.

To this day, Trump has offered no plausible plan to replace the ACA or protect the tens of millions of Americans who suffer from pre-existing conditions and would once again be subject to discrimination by the insurance industry. That is not his concern.

Repealing the law informally named for his predecessor, like building a wall at Mexico's expense, was a major applause line for the Republican base in Donald Trump's march to the nomination in 2016. And if one thing has become abundantly clear about this President, it's that the base must be served -- first, last and always.

That's why destroying the Affordable Care Act -- or getting caught trying -- has become a political imperative. He tried and failed to kill it in Congress. He has done his best to strangle it administratively. Now, overruling both his attorney general and his secretary of health and human services, according to reports in the New York Times and Politico , he is determined to thwart it in the courts.

Trump shut down the government over the wall. There is no doubt that he would cut millions off of insurance to redeem his promise to the base to demolish Obama's health law.

When the ACA was passed nine years ago, I sobbed, knowing that other families would be spared the agony mine had known. I have met many of them in the intervening years. And I mist up all over again.

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I've written before about the exchange I had with President Barack Obama the night the ACA passed. I thanked him on behalf of families like mine, with children who had pre-existing conditions. He simply replied, "That's why we do the work."

For Donald Trump, politics means something entirely different. It's about the acquisition and execution of power for his own aggrandizement. Trump is about winning, and he believes that stoking his base is what got him to the White House and will secure for him the chance to stay.

On this issue, though, he has badly miscalculated. Every American knows someone, and perhaps loves someone, with a chronic illness. Now Trump has ensured that the threat to people with pre-existing conditions will be front and center in yet another campaign.