RSP is an ETF designed to track the S&P 500 Equal Weight Index, which holds the same S&P 500 constituents but resets each stock back to an equal weight at quarterly rebalances. That structure reduces concentration in mega-cap technology and increases exposure to the median/typical S&P 500 stock, making day-to-day performance more dependent on market breadth and sector rotation than cap-weighted benchmarks. (spglobal.com)

There is no single RSP-specific headline catalyst; the move is best explained by a rotation-heavy tape where leadership has been shifting between defensives (utilities, staples, parts of real estate) and weaker mega-cap technology. In sessions like this, RSP can trade differently than SPY because it is less dominated by the largest tech stocks and more influenced by how the broader list of S&P 500 constituents behaves. Today’s broad market tone is slightly risk-off, with cap-weighted benchmarks also softer, consistent with a rotation rather than an ETF-specific shock. (monexa.ai)

RSP tends to benefit when market breadth improves (more stocks participating) and can lag when performance is narrowly driven by a handful of mega-caps. Investors should monitor whether the market continues to reward defensives versus growth/tech and whether rate expectations and Treasury yields keep pressuring duration-sensitive equities, since those forces can quickly flip the relative performance of equal-weight versus cap-weighted S&P exposure. (research2.fidelity.com)