U.S. Stocks are down as mixed data come in from auto sales, the release of weak August construction spending, and better-than-expected manufacturing data hit the markets on Monday. The ISM manufacturing index for September came in at 51.5, slightly higher than the consensus of 50.2. Construction spending in August declined 0.7% from July, missing expectations. On a year-over-year basis, spending on home building declined 0.3%. Twitter's shares rose in trading Monday on a report that Alphabet hired an adviser to help evaluate a bid to acquire the social media company. Tesla shares rose after reporting its best sales quarter ever, saying global deliveries of its cars more than doubled in the third quarter to 24,500 from a year earlier. Finally, Ford's stock increased after reporting U.S. sales declined 8% this month, but the company said September was the best month for its F-Series retail sales. TheStreet's Valerie Young reports from Wall Street.