A long list of health care experts says the Republican bill to dismantle most of President Obama’s health insurance program would be a disaster. The American Medical Association is against it. Insurance providers are against it. Patient groups are against it. Sen. Bill Cassidy’s bill, coauthored with Sen. Lindsey Graham, would cut federal spending on Medicaid by amounts one consultant called “jaw-dropping.” If the bill passes, 21 million fewer people would have health insurance in 2026 than under current law, according to a study by the Brookings Institution and USC.

To which Cassidy says, in effect: Pay no attention to the experts. “More people will have coverage,” he promised last week. “And we protect those with preexisting conditions” — another claim many have contested.

It would be nice if we could turn to a trusted, nonpartisan referee to sort out these conflicting claims — something like the Congressional Budget Office, whose director was appointed by Congress’ Republican leaders to provide nonpartisan advice in just this kind of situation.

But Cassidy and Graham threw their proposal together so quickly that the CBO hasn’t had time to study it. The budgeteers are scrambling to deliver a bare-bones report next week, but it won’t include estimates of the bill’s effect on insurance coverage, premiums or the federal deficit — which was pretty much the main point.

Congress normally waits for those numbers before voting on an important bill like this. It also usually holds hearings to ask experts what they think. But with a Sept. 30 deadline under the rule that allows them to pass a bill with only 50 votes, Senate leaders decided to dispense with the niceties and plunge ahead.

As one GOP senator acknowledged, this bill is important mainly as an act of political symbolism — never mind that it would reshape the health care of millions of people.

“You know, I could maybe give you 10 reasons why this bill shouldn’t be considered,” Iowa Sen. Charles Grassley, a crusty GOP elder, told reporters with disarming candor. “But Republicans campaigned on this so often that you have a responsibility to carry out what you said in the campaign. That’s pretty much as much of a reason as the substance of the bill.”

On one level, this is just another story of partisan polarization and the erosion of the Senate’s tradition of slow, bipartisan legislating — the “regular order” Sen. John McCain complained was missing when he announced Friday that he would vote against the bill.

It’s another step, as well, in the creeping marginalization of the CBO, which Republicans have grown to hate because its nonpartisan experts often deliver unwelcome news. Former House Speaker Newt Gingrich has derided the budget office as “corrupt” and called for its abolition, even though its current director is a Republican appointee. That conflict will continue as the Trump administration tries to steer a big tax-cut bill through Congress this fall.

In a broader sense, this is also a story about what some scholars have dubbed “the death of expertise”: the increasing willingness of politicians and ordinary citizens not only to dismiss what experts say, but to brand it as partisan claptrap if they disagree.

That’s not entirely a new phenomenon. The historian Richard Hofstadter wrote about it in his 1963 classic “Anti-Intellectualism in American Life.” But it has clearly escalated in recent years as partisan think tanks on both right and left have joined older, nonpartisan institutions in the battle of ideas, and as partisan cable networks have broadcast each side’s arguments more widely with little regard to objective reality.

President Trump has contributed too, by rejecting propositions most other people consider to be facts. He once claimed that climate change was a hoax invented by China; and he has insisted that millions of people voted illegally on election day.

In this environment, it makes a certain kind of sense that a nonexpert has become the most effective spokesman for the fact-based health care opposition: ABC late night host Jimmy Kimmel, whose infant son underwent open-heart surgery on his first day of life.

He argued on his show that Cassidy’s bill flunked the “Kimmel test” — that it would not guarantee health care to any child who needed it, regardless of family income.

Cassidy said Kimmel was wrong, and some on the right told Kimmel to leave policy to the policy wonks. But as if that weren’t ironic enough (given that Republicans have done their best to ignore the experts), the wonks have generally sided with Kimmel against Cassidy.

“More people will have coverage,” Cassidy promised.

Quite the opposite, say almost all of the nonpartisan experts.

“We protect those with pre-existing conditions,” Cassidy added.

Except his bill includes a provision under which states can allow insurers to charge higher prices to people with health problems.

As Cassidy noted in a March op-ed column, it’s important to get the facts right. “Ronald Reagan said that everyone is entitled to their own opinions, but not to their own facts,” the senator wrote.

Actually, Reagan didn’t say that. Daniel Patrick Moynihan, the Democratic senator from New York, did. But it was still the right idea.

Doyle McManus is a columnist for the Los Angeles Times.