April 25 (Reuters) - Star host Tucker Carlson's abrupt exit from Fox News is likely to hit short-term ratings but could nudge more mainstream advertisers to consider a network they have snubbed for being too partisan, investors and analysts said. News of his departure on Monday wiped nearly $1 billion from the market valuation of the network's parent company, Rupert Murdoch-controlled Fox Corp (FOXA.O). "It's a huge deal," said Matthew Tuttle, head of Tuttle Capital Management, an investment firm that is betting against Fox shares. The conservative-leaning Carlson's prime-time show was the highest-rated cable news program in the key 25-to-54 age demographic on Fox News - the most-watched U.S. cable news network. It's likely that advertisers who were seeking that audience may have limited other options for conservative news viewership without skewing too conservative."

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