Christmas beckons, and the retailers are quietly humming “Jingle Tills,” their favorite carol.

Holiday spending accounts for about $600 billion a year, or nearly a fifth of retailers’ $3.2 trillion in annual sales, according to the National Retail Federation.

Investors in retail stocks are betting on the best holiday shopping season in years. Retail stocks from Tiffany & Co. TIF, -1.17% to Nordstrom JWN, -7.45% to Macy’s M, -6.65% to Wal-Mart WMT, +0.41% have recently surged to record highs.

The NRF is predicting a significant jump in holiday spending. It reckons sales will be up 4.1% this year, the strongest growth since 2011 and way above the average this millennium.

But is there a Grinch lurking in the hills high above Whoville?

There may be: A Grinch in the shape of a giant iPhone.

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That, at least, is according to some new research by analysts at Canaccord Genuity.

Their take: Spending on new iPhone 6 and iPhone 6 Plus phones from Apple AAPL, +0.52% is going to vacuum up so much of consumers’ money that the rest of the retailers may be in for a much tougher time than they realize.

“We estimate iPhone 6 upgrades and purchases will equate to $4 billion in retail sales in November and December,” warns Canaccord analyst Camilo Lyon in a new research paper. That, he says, equates to “approximately 16% of the $24.3 billion in incremental dollar growth expected this holiday season.”

Or, to put it another way, while Apple is likely to see a sales boom, the rest of the mall will be left with a much more modest increase in sales of around 3.3%, says Canaccord.

Different analysts may play with different numbers for sales of iPhone 6s. And the amount consumers spend will depend to some extent on whether they get subsidized iPhones now, and pay higher mobile fees each month over the next two years, or pay the full cost of the iPhone upfront and then shop around for a cheaper mobile deal.

(Read How to save hundreds of dollars on your next iPhone.)

But even though different people will quibble about the numbers, the analysis is surely “directionally correct,” as we used to say at McKinsey & Co. Surging sales of new iPhones are going to take a lot of the dollars that consumers are going to spend this holiday season.

And that has big implications beyond those for Apple itself.

It may be good news for those hunting for bargains this holiday season. You might want to hold off for a little to see if you can get a deal. If retailers find Apple is stealing their customers, you can expect them to respond with some aggressive discounting to shift the inventory.

Meanwhile investors in retailers might want to double-check their numbers. Many stocks look in line with modern averages when you compare them to forecast per-share earnings, but that assumes they come through with the earnings.

Or maybe consumers will buy iPhones and spend freely in other stores, and let that magical plastic take the strain. According to the Federal Reserve, total revolving consumer credit—mostly credit cards—rose 3.3% in the third quarter, and now stands at the highest levels since 2009.