NEW YORK (CNN/Money) - A lot of last year's biggest stock market highfliers have lately been doing excellent Howard Dean imitations. And it's unclear whether they can regroup and take Wisconsin.

Williams Companies, which ran up 263.7 percent last year, has dropped 12.1 percent from its January high. PMC-Sierra, a 261.5 percent gainer in 2003, is down 16.7 percent from its best level of this year. Corning, which tacked on 215.1 percent in 2003, is off 14.2 percent from last month's highpoint.

And so on, on down the list. Meanwhile everyone's favorite proxy for speculative excess, the Nasdaq Composite, is down 6.2 percent from its best January close and is now up only fractionally on the year.

So maybe momentum has finally left the building, but why now?

Ever since the summer, at least, there have been hosts of sober-sounding portfolio managers saying that these stocks had run far ahead of their fundamentals to levels that were plainly ridiculous. Shouldn't the selling have happened then?

Clearly a lot of these folks weren't so stolid as they made themselves out to be. After the late-1990s debacle, not many people are willing to get on TV and say that even though Sanmina is already up 100 percent on the year, they're backing up the truck and buying more -- even though they are backing up the truck and buying more.

It helped, also, that a lot of hedge funds -- many of them fairly greenhorn -- had developed a knee-jerk habit over the past few years of betting against these stocks. A heavy short position can lead to outsized gains in a stock, because as it moves higher, short sellers are forced to buy back the shares they borrowed and sold

But with the beginning of a new year, those hedge funds aren't such a factor anymore. Many have rejiggered by now, covering their shorts, putting bets elsewhere. The dedicated short funds aren't likely to pull in much money. Some funds that faired poorly last year have cut back staff; some are closing their doors.

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In the meantime, the happy-go-lucky mutual fund managers all know, or think they know, that they're not going to be able to rack up big points buying the Broadcoms of the world this year. So they are shifting money elsewhere.

Yet that doesn't mean that the highfliers are down for the count. Investors have a proclivity for putting money into the stocks that have performed best, and many of them are doubtless kicking themselves for missing last year's big movers.

If the overall market regains its footing over the next few weeks, the recent declines in these stocks are going to smell like opportunity to a lot of investors.