THIS TIME, THE CREAM ISN'T rising to the top.

The historic rally that has lifted the Standard & Poor's 500 index by 50% from its March lows has been led by economically sensitive and lower-quality stocks, including such sectors as financials, basic materials, retailers and industrials. By contrast, high-quality stocks like Abbott Laboratories (ABT), ExxonMobil (XOM) and Procter & Gamble (PG) generally have lagged, with many showing outright losses so far this year.

The rush by investors for cyclical, economically sensitive stocks has only increased as the outlook for the global economy has brightened. But now a shift may be at hand. While it's tough to time changes in investor sentiment, quality stocks soon could start to shine.

Several factors are...