There is no doubt that Hillary Clinton received a sizable bounce from the Democratic convention. Sean Trende says that Clinton’s position in the polls appears to have improved by at least six points, though some of the improvement may be due to Donald Trump’s dispute with the parents of a dead war hero, rather than the Dems’ convention per se.

Trende asks whether the bounce will last. He notes that “second convention bounces tend to fade; it did for the Republicans in 2004 and 2008 (even before the Lehman Brothers collapse); it did for the Democrats in 1996.”

On the other hand, George H.W. Bush’s 1988 second convention bounce did not fade. Down by nearly 20 points to Michael Dukakis going into the GOP convention, he came out of that event ahead and more or less cruised to a convincing victory.

Clinton’s bounce may fade too, but I don’t think it will. Why? Because the bounce, like Bush’s, was built on the most obvious truth in this year’s election. Bounces based on half-truths well presented tend to fade. Bounces based on an obvious and crucial truth don’t.

The obvious truth that sustained the senior Bush’s bounce was that Ronald Reagan’s presidency had been a big success, a point Reagan himself drove home brilliantly in his convention speech. The obvious truth in this year’s election is that Donald Trump isn’t fit for the presidency, a point driven home in several strong speeches last week and reinforced by Trump himself immediately after the convention.

Hillary Clinton is also unfit for the presidency. She’s corrupt; she jeopardized national security; she botched several key decisions as Secretary of State; her temperament is lousy.

But Trump’s unfitness is even more obvious. Unlike Clinton, he can’t discuss most issues knowledgeably. Unlike Clinton, he cannot behave himself. Unlike Clinton, he cannot conceal his viciousness.

Unlike Clinton, he lacks any of the credentials normally associated with a serious candidate for president — e.g., experience in Congress or experience in the Cabinet. Indeed, Trump has no experience in the realm of public service or in the formulation of public policy. (Note: this doesn’t mean I consider Clinton preferable to Trump; for me, Clinton’s leftism makes Trump the lesser of the two evils — whether he’s “lesser” enough to vote for is a question I’m still considering.)

Moreover, Trump played right into the narrative the Democrats laid out so well at their convention when he became embroiled in a controversy with the Khan parents. In her acceptance speech, Clinton had called Trump unfit for the presidency because he can’t even resist being goaded into Twitter wars.

Before the dust could settle, Trump basically proved Clinton’s point.

It reminded me of when Chris Christie told a debate audience that Marco Rubio repeats the same canned points over and over, and Rubio promptly obliged by doing just that. The big differences: (1) Rubio made this mistake in the heat of a debate; Trump did it at his leisure and (2) using canned talking points doesn’t make one unfit to be president.

Can Trump bounce back? It won’t be easy. I expect there will be more instances of terrorism both at home and abroad. But the public’s understanding that Obama and Clinton have been terrible on this issue is already firm. More of the same kind of terrorism is unlikely to change the dynamic of this race. If, God forbid, there’s a massive attack here, then all bets are off.

The debates could change the dynamic of the race. If, as I expect, Hillary goes into them with a big lead, she will play it safe. This might enable Trump to get the jump on her in the first debate, as Mitt Romney did with President Obama. But my guess is that it will take outstanding performances from Trump and weak performances from Clinton to tilt the race to the tycoon, if Clinton is well ahead going in.

Clinton is no debate star, but her performances against Bernie Sanders were rarely weak. As for Trump, he will be Trump. The Democratic convention left most Americans with the conviction that this will not do.