Investors will follow every move from European leaders on the road to Friday's EU summit, and financial markets will feel every bump along the way.

That certainly was the case Monday when the Dow was up as much as 167 points but gave back half of those gains, after reports that Standard & Poor's could put the members of the euro zone on credit watch for possible downgrade. Standard & Poor's, after the close, did say it was putting 15 countries, including Germany, on credit watch because of tightening credit conditions, the risk of recession , high debt levels and continued disagreement among European officials about how to tackle their sovereign crisis .