Stocks are on their strongest run since the bear market started a year and a half ago as investors continue to debate whether the economy and the markets have finally stabilized.

The Dow Jones Industrial Average climbed 174.75 points, or 2.3%, to 7924.56. The Dow is up 21% from its closing low on March 9, a gain which technically pushes the blue-chip benchmark into bull-market territory. The jump surpasses the near-20% rally from Nov. 20 to Jan. 2, which was formerly the biggest rally during a bear market that began in October...