Stocks surged on Monday, with the Dow and the S&P 500 posting their best one-day advance in nearly five months, after the Obama administration unveiled a long-awaited plan to purge toxic assets from bank balance sheets.

A report showing a rebound in existing-home sales in February added to the positive tone.

The Dow Jones industrial average <.DJI> gained 497.48 points, or 6.84 percent, to 7,775.86. The Standard & Poor's 500 Index <.SPX> rallied 54.37 points, or 7.07 percent, to 822.91. The Nasdaq Composite Index <.IXIC> surged 98.50 points, or 6.76 percent, to 1,555.77.

(Reporting by Rodrigo Campos; Editing by Leslie Adler)