RSP Flashes Breadth Warning: Is the S&P Rally Built on Sand?

The S&P 500 looks fine on the surface. $SPY found support at its 50-day moving average and even posted a gain on the day. Nothing to see here, right? Wrong. Investor's Business Daily's Mike Webster is waving a yellow flag, and it's not about the headline index at all. It's about what's happening underneath it.

Webster's preferred breadth gauge is $RSP, the equal-weight S&P 500 ETF, which treats Apple the same as Whirlpool. And right now, RSP is stuck below its 21-day moving average for several consecutive sessions, which Webster reads as a confirmed trend change to the downside. The divergence between SPY (propped up by mega-caps) and RSP (representing what the average stock is actually doing) is the kind of thing that tends to matter a lot right before it matters catastrophically.

It gets messier when you zoom out. Over on TheChartGuys' FOMC preview, the same picture emerges: NASDAQ, the S&P 500, and most major sectors are stuck in tightening, constricting ranges. The market is pricing in an 87% probability of a rate hike at the upcoming Fed meeting, which paradoxically makes a hike the less volatile outcome. A no-hike surprise would likely trigger a sharp bullish repricing and a lot of confused traders asking where their short positions went.

The sector breakdown makes the breadth concern more credible, not less. Industrials, transportation, and materials are all showing weakness. These are the cyclical bellwethers that tend to sniff out economic softness early. Even within the NASDAQ, the story is fractured: software ETF $IGV is weakening, the semiconductor ETF $SMH is in a tight equilibrium, and while $MAGS remains the strongest component, Nvidia has double-topped near all-time highs, which is exactly the kind of setup that makes technical traders nervous.

The Felix and Friends crew over at Goat Academy added an interesting behavioral layer to all of this. A live poll asked viewers where they would sell Alphabet, then revealed Berkshire had nearly doubled its stake. Instantly, poll respondents changed their sell targets. The lesson: even disciplined retail traders abandon their exit rules the moment a famous name enters the picture. In a market held together by large-cap concentration, that kind of herd behavior around a handful of mega-cap names is worth keeping an eye on.

When the engine of your rally is three or four stocks, and the average stock is quietly rolling over, you are not in a bull market. You are in a magic trick.