Shortly before the Republicans’ domestic policy megabill cleared Capitol Hill, there was compelling evidence that Donald Trump didn’t know what was in his inaptly named One Big Beautiful Bill Act. One GOP senator said in late June, for example, that he’d spoken to Trump about some of his concerns, and the president was surprised to learn about some of the bill’s contents.

Soon after, the day before the final vote in the House, NOTUS reported: “Trump still doesn’t seem to have a firm grasp about what his signature legislative achievement does.”

But as it turns out, the president has some company. My MSNBC colleague Hayes Brown highlighted one of the more notable and mysterious aspects of the far-right reconciliation package.

There’s a mystery afoot on Capitol Hill. Tucked within the Republican megabill President Donald Trump signed on July 4 was a tax provision that surprised most, if not all, of the Republican members of Congress who voted for it. The provision limits the amount gamblers can deduct from their income taxes based on their losses — and nobody seems to know how it got into the bill.

HuffPost published a great report along these lines this week, noting the responses from GOP senators who were dumbfounded when asked about the gambling-related provisions in the bill they’d already passed. “If you’re asking me how it got in there, no, I don’t know,” Republican Sen. Chuck Grassley of Iowa said. Republican Sen. John Cornyn of Texas added, “I don’t know anything about it. I’m not sure what it does.”

The reactions from Grassley and Cornyn were of particular interest because both serve on the Senate Finance Committee, which was chiefly responsible for crafting the tax policies in the GOP megabill.

Why didn’t the changes to gambling deductions catch their eye during committee hearings and the markup process? Because the Senate Finance Committee didn’t hold committee hearings and largely skipped the markup process. Republicans, eager to meet Trump’s July 4 deadline, simply rushed the massive legislation to the floor, without reading it.

Lawmakers are exploring ways to undo what they just did, but as that process unfolds, it’s worth pausing to look at this as a learning opportunity on Capitol Hill: Reading bills, especially important ones with transformative impacts, tends to be a good idea.

It’s a lesson a variety of members have confronted as of late. Republican Rep. Marjorie Taylor Greene of Georgia, for example, recently expressed outrage over provisions in the bill related to regulating artificial intelligence — after she’d already voted for it.

A week earlier, Republican Rep. Mike Flood held a town hall meeting with constituents in his Nebraska district, where he faced questions about a provision in the bill related to the judiciary. Flood agreed that the underlying policy (which was later removed) was misguided, while grudgingly conceding that he didn’t know it was in the bill he voted for.

There are a variety of recent examples of congressional Republicans disagreeing with the bill they voted for and even talking about efforts to change it, but the question about whether GOP policymakers read the bill they passed is qualitatively different — and noticeably worse.