Another week, another set of polls showing Donald Trump with a huge edge over his opponents for the Republican presidential nomination. And a dive into the numbers shows that the former president’s lead may be more durable than the ones leading presidential candidates have enjoyed in past summers.

Quinnipiac’s latest national poll puts Trump’s GOP support at 62%, a full 50 points ahead of his nearest foe, Florida Gov. Ron DeSantis. A new Washington Post/Monmouth survey of the first-in-the-South primary state of South Carolina has Trump at 46%, with former South Carolina Gov. Nikki Haley a distant second at 18%. That lead is even more imposing when you consider that both Haley and Sen. Tim Scott, also from South Carolina, have won multiple elections there. And yet their combined share of support in the South Carolina poll — 28% — is just over half of Trump’s.

By now, there’s nothing new or particularly surprising about numbers like these. Since April, Trump has been steadily polling above 50% in rolling national averages and established formidable leads in key early states. Our own NBC News/Des Moines Register/Mediacom poll, for instance, gave Trump a 42%-19% advantage over DeSantis in Iowa last month.

It’s been awhile since a nonincumbent GOP candidate enjoyed polling leads this large and sustained at this point in the campaign. To find a parallel, you have to go back to the fall of 1999, when then-Texas Gov. George W. Bush was sitting on Trump-size leads nationally and in the early states.

Bush, of course, went on to win the nomination, though not without a real scare. He ended up getting crushed in New Hampshire by John McCain before surviving a make-or-break battle with McCain in South Carolina, only to turn around and suffer an upset defeat in Michigan, and then — finally — steady the ship enough to win a series of big states on Super Tuesday and force McCain’s surrender.

In other words, what looked in the fall of 1999 like a glide path to the GOP nomination turned into a bruising and politically costly primary battle for Bush, one that arguably damaged his image with general election voters and nearly cost him in what ended up being a razor-thin victory over Democrat Al Gore.

So, on the surface, the case of Bush and the 2000 Republican primaries offers a glimmer of hope to Trump’s rivals, who are staring at polls that look just as gruesome for them now as they did for Bush’s foes at this point in the ’00 cycle.

But inside the numbers, there’s a key difference, one that suggests Trump may be far less vulnerable to the kind of slippage that Bush ultimately suffered.

It has to do with how many Republican voters are telling pollsters that their minds are already made up and that they definitely plan to vote for the candidate they now support. That’s where we see significant differences between Trump’s standing now and Bush’s in the fall of 1999.

Let’s start with the national polling. This week’s Quinnipiac poll has Trump at 62%, DeSantis at 12% and the rest of the field in single digits.

A CNN/SSRS national poll last week that found a similar, though not quite as overwhelming, Trump edge, with him at 52% to DeSantis’ 18% ahead of the single-digit brigade.