Merriam Webster defines smoking gun as "something that serves as conclusive evidence or proof (as of a crime or scientific theory)." In politics, it has often been used to describe evidence that sways even members of the party of the person under investigation.
Most notably, "smoking gun" was used to describe the release of tapes from Nixon's Oval Office conversations immediately following the 1972 break-in at the Democratic National Committee’s headquarters at the Watergate Office Building. In particular was one that captured a discussion between Nixon and his chief of staff H.R. Halderman. The two discussed asking the head of the CIA to put pressure on the FBI director to halt the bureau's investigation into the Watergate break-in because it was a national security matter. On August 4, 1974, the tape of that discussion was made public.
At that point, Nixon’s remaining political support on Capitol Hill all but disappeared. The 10 Republican members of the Judiciary Committee who had voted against impeachment in committee announced that they would now vote for impeachment once the matter reached the House floor.
Nixon lacked support in the Senate as well. Sens. Barry Goldwater (R-Ariz.) and Hugh Scott (R-Pa.), the minority leader, told Nixon that no more than 15 senators were willing to even consider an acquittal.
But that was 47 years ago. Things have changed. If you're waiting for a smoking gun to bring down Trump and his enablers, it is beyond time to recognize that it isn't going to happen. That's not because there is a lack of conclusive evidence that the former president and his allies repeatedly obstructed justice, abused power, incited a riot at the Capitol, and attempted a coup to overturn an election. Instead, it is because no amount of evidence is going to shake Republican support.
On January 13, Kevin McCarthy said, "The president bears responsibility for Wednesday's attack on Congress by mob rioters." Similarly, Mitch McConnell made it clear that "There's no question, none, that President Trump is practically and morally responsible for provoking the events of the day." Even so, neither of these Republican leaders have done anything to hold the former president accountable. Instead, they've done everything in their power to protect him from the consequences of his actions.
I suspect that most Republican politicians know the danger Trumpism poses to our country. But they also know that, with the grip the former president has on the GOP, taking him down would mean that the entire party goes with him. That's not something they're willing to risk. As Jamie Raskin pointed out, "fascism is not an ideology; it’s just a strategy for taking power and maintaining it.”
The one thing the fascists have today that Nixon didn't is the epistemic closure created by an entire network of right wing news outlets. They create a path for the fascists to take, while providing cover for criminality. As long as Republican voters buy into that distorted reality, their leaders won't challenge it. In other words, there is a self-reinforcing feedback loop between right wing media, Republican voters, and GOP leaders. Anyone who dares to step out of that loop (ie, Liz Cheney) is vilified and excommunicated from the cult.
All of that is why there will never be a smoking gun that brings the whole thing down. I am reminded of the fact that, prior to the 2016 election, we all heard audio tape of Trump bragging about being able to "grab p***y." That didn't stop almost 63 million Americans from voting for him. The one time he told the truth was when he said that he could shoot someone on 5th Avenue in broad daylight and his supporters wouldn't abandon him...even as he held the smoking gun.