Jolly old Saint Nick hasn't arrived yet on Wall Street, but he's due any day now. At the risk of going out on a limb, it looks to me as if the massive tax-related selling that has depressed stock prices for the past few trading sessions is about to dry up. Odds are that the market will improve in the second half of the month.

On the face of it, today's trading wasn't too pretty. More stocks declined than advanced, by a wide margin, on all three major exchanges. In addition, as they've done for months, the poor, battered financials bore the brunt of the selling.

As the session wore on, however, the bears failed to knock the S&P down through support around 1470. A nice little rally ensued in the last three hours of trading. Perhaps now investors will take a second, more sympathetic look at the Fed's actions earlier this week -- and give the market its traditional December boost.

Historically, December is the best month of the year for stocks. Since 1945, the S&P 500 index has risen in 48 Decembers and fallen in just 14, for a 77% success rate.

Moreover, the December record is even more impressive after a down November. (Need I remind you: Last month, the S&P sank 4.4%.) Since 1945, the S&P has fallen 21 times in November. After those drops, the market went on to record an uptick in 19 Decembers -- a remarkable 90% of the time. Only during the recession years of 1969 and 1974 did stocks fail to bounce in December after a November slide.

If I'm right about a strong second half to the month, which stocks should perform best? Probably those that have been beaten down the most in recent days. Top of my list, for a trade anyway, would be Sallie Mae (NYSE: SLM), the nation's largest originator of student loans.

Yesterday, SLM announced that its troubled buyout deal with a consortium of private-equity funds fell through. I'm disappointed, of course, because I felt that the consortium's last offer ($50 per share plus warrants) would have given us a respectable return on our money.

But the drop in the stock over the past few weeks, and especially in the past three days, looks like an extreme overreaction. Even with SLM's lower earnings guidance for 2008 (also announced yesterday), the company is surely worth more than 10 times a depressed year's profits. In 2002, amid a ferocious bear market, SLM averaged 19X earnings.

This is the kind of stock that could rally 20% in a heartbeat once the disillusioned holders clear out.