There’s a dynamic developing in the presidential race that’s very dangerous for Donald Trump.

New polls are coming in with increasingly dismal news for the GOP nominee. He now trails Clinton by 8.9 points in a head-to-head national matchup, on average. If that margin holds up, it would give Clinton the biggest popular vote victory in a presidential race since Ronald Reagan’s 1984 landslide.

That’s all bad enough news for Trump in itself. But these polls have effects that will ripple outward, and could turn a possibly temporary poll decline into a permanent one.

Polls can play two roles in a campaign. One is as a reflection of the electoral reality. The other, less common role is as a driver of the electoral reality. In Trump's case, the recent spate of bad polls might be doing exactly that — changing the context in which Trump operates, as opposed to simply describing it.

Specifically, these polls could be driving more and more Republicans to abandon a Trump campaign that looks increasingly like a sinking ship.

That newfound spectacle of increasing GOP defections from Trump then helps advance the Clinton campaign’s narrative that he’s a candidate who is not like ordinary Republicans — that he’s deeply unusual in some scary ways.

And if more voters are convinced by that argument, Trump’s support among the electorate will continue to decline, and his bad polls will get even worse.

The self-perpetuating cycle of bad polls for Trump and GOP defections from him

This cycle starts off with bad polling news for Trump. This cements the perception that he’s very likely to lose, and as a result, more and more Republican elected officials, staffers, and donors become emboldened to come out against him.

Some of these actors, facing electorates with Trump-hostile populations either this year or eventually, will try to flee the sinking ship to save themselves. Others will try to curry favor with the likely next president, Hillary Clinton. And others will want to position themselves on the right side of history — or at least the right side of a coming intraparty showdown over who gets the blame for Trump’s defeat.

We are already seeing this take place. In the past week, several GOP members of Congress have moved from studied silence on Trump to outright condemnation of his candidacy. Sen. Susan Collins of Maine announced she wouldn’t vote for Trump in an op-ed. Rep. Scott Rigell of Virginia endorsed Gary Johnson. Rep. Charlie Dent of Pennsylvania said Trump had gone "too far" to earn his vote.

As this goes on, more and more wealthy Republican donors are now openly backing Clinton too. Of course, Trump’s lack of support from billionaires didn’t hurt him in the primary, when he mostly self-funded his campaign. But Trump isn’t wealthy enough to fund a national general election campaign on his own, so he’s embraced traditional political fundraising in the past few months, and his July tally was viewed as surprisingly strong.

Donors don’t want to throw away money on a loser, though — especially reluctant conservative donors who were never big fans of Trump anyway. So if he goes down, they’ll put more and more of their money toward attempting to mitigate GOP losses further down the ballot, which could starve the Trump campaign of funds, hurting his turnout efforts and limiting his ad buys (though he could make up some of the deficit with small-donor cash).

Meanwhile, we’ve also seen more members of the GOP’s foreign policy brain trust denouncing Trump in remarkably strong language, as 50 former officials who had served in Republican administrations did in a letter Monday.

Voters may not notice these defections on their own, but each new one creates one more example that gets media attention and can be used to confirm a larger story that the Clinton campaign is trying to tell about Trump — that there’s something uniquely bad about him that makes him unfit to be president, so much so that even his own party members are rejecting him.

So Trump’s hemorrhaging of internal party support could well ripple outward, to voters — making his already bad poll decline even worse and creating a self-perpetuating cycle to drag him down further.

Trump needs to be a generic Republican to win. But there’s nothing generic about Trump.

Now, you may think that Republican defections from Trump could actually help his candidacy, as seemed to happen during the primaries — perhaps it would demonstrate his independence from the two parties.

But there are many indications at this point that the more voters view Donald Trump as a generic, mainstream, ordinary Republican, the more likely he is to win.

Several political science forecasting models based on economic conditions and other "fundamentals" say the GOP should have the advantage this year. And Hillary Clinton remains rather unpopular even after her successful convention — the problem for Trump is that he’s far more unpopular.

You can see this at play in swing states, where Republican Senate candidates who are viewed as more generic are consistently outperforming Trump in polls, sometimes by double digits. And a new poll from Monmouth University finds that Clinton is winning 92 percent of Democratic voters, while Trump is only winning 79 percent of Republicans — that is, he’s not doing as well as a generic Republican should.

That’s why there’s been a deliberate effort from GOP elites, and occasionally the Trump campaign, to advance the fiction that Trump is a completely ordinary, mainstream GOP nominee.

Mike Pence was a boring, un-Trump-like VP choice made, in Trump’s own words, for "party unity." And the Republican convention three weeks ago was an extended exercise in pretending things were normal, with party leaders from Reince Priebus to Paul Ryan to Mitch McConnell playing along with the fiction that Trump is an ordinary, generic Republican and only Ted Cruz going off script.

When Democrats met for their own convention the following week, they did their best to dispel the fiction that Trump is normal. Key speakers from President Obama to Hillary Clinton made the case that something is very different and scary about Trump — that his divisive style and temperament make him unfit for office.

But it took Trump himself to truly blow things up with his attacks on the Khan family. Though the first batch of polls that came in after the Democratic convention were good for Clinton, it was only after several days of raging controversy over the Khans that she started posting truly eye-popping numbers, as voters were seemingly repelled by Trump’s behavior.

You can see in Collins’s strong language denouncing the nominee that she was eager to pretend Trump could be an ordinary candidate, a generic Republican — until the Khan attacks convinced her that was impossible.

"The unpleasant reality that I have had to accept is that there will be no ‘new’ Donald Trump, just the same candidate who will slash and burn and trample anything and anyone he perceives as being in his way or an easy scapegoat," Collins writes. "Regrettably, his essential character appears to be fixed, and he seems incapable of change or growth."

Now, don’t expect the GOP to abandon Trump en masse. He is still popular among the party’s base voters, as we can see in recent polling showing Cruz’s popularity among Republicans plummeting after his defiance of Trump at the convention. And there are still a whole lot of big names choosing silence or ambiguity rather than outright condemnation.

But Trump risks a very real tip into a possible spiral that could be very bad for him. And if we get to the point where GOP senators in swing states like Pennsylvania and New Hampshire are openly attacking their party’s nominee, that will be a sign that Trump truly is done for.

Watch: The bad map we see every presidential election