Wachovia downgrades CBS Corp. stock

Cites challenging advertising market as one factor

Wachovia on Wednesday downgraded shares of CBS Corp. to "market perform" from "outperform" even though the company had reported stronger-than-expected first-quarter earnings on Tuesday.

The brokerage argued a challenging advertising market combined with the company's strategy of acquiring growth will limit upside potential for the stock in the near-term. While CBS' TV unit exceeded financial expectations, much of the upside was due to a change in syndication rather than underlying strength, Wachovia said.