The Trade Desk, Inc. TTD is trading higher Tuesday after the digital advertising company announced that it would be added to the S&P 500 Index. This is considered a bullish dynamic because it expands the number of institutional investors who can invest in the stock.There is a chance it is about to fill a gap. This could mean a rapid move higher. It is why The Trade Desk is our Stock of the Day.As you can see on the chart, the shares have run into resistance around $85.50. This isn't a coincidence. On Feb. 1 ...