Charles Schwab's (SCHW) - Get Report chief investment strategist, Liz Ann Sonders thinks the bull market has some steam left. 'No one has been a big believer in this bull market and that's a positive,' she said. 'One of the reasons why we have remained fairly constructive this entire bull market is because of how many disbelievers there are. I think the sentiment environment is probably the most important prop for the market.' Plus, the U.S. Citigroup Economic Surprise Index, which tracks whether economic data has been worse or better-than-expected, has risen in the past month, sending the S&P 500 higher. TheStreet's Scott Gamm reports from Wall Street.