Jim Cramer has been talking about the upside potential of Citigroup ( C). He thinks that the change in mark-to-market might set up the short-squeeze opportunity of a lifetime in the stock.

A short squeeze takes place when short-sellers scramble to cover their bearish positions on optimism or any positive catalyst, driving the price of stocks up sharply. The metric for measuring short-squeeze opportunities is the short ratio, which is the number of days it would take the short-sellers to cover their positions based on recent average daily volume.

Citigroup isn't the only stock that has short-covering upside potential. With this in mind, Stockpickr has compiled a portfolio of the top S&P 500 short-squeeze plays.

To read more, visit Stockpickr.com.

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