Carl Icahn's audacious bid to overthrow Yahoo's board could bring Microsoft back to the bargaining table and revive the tech megamerger.

On Thursday, the billionaire investor instigated a plan to expel Yahoo's board of directors for "irresponsible" and "unconscionable" acts that prompted Microsoft to drop a $47.5 billion bid to buy Yahoo.

In a letter to Yahoo Chairman Roy Bostock, Icahn says outraged Yahoo shareholders urged him to lead a campaign to replace Yahoo's 10 directors at the company's July 3 shareholders meeting.

He has plenty of supporters.

Paulson & Co., the $30 billion hedge fund that has built up a stake of about 50 million shares in Yahoo in recent months, says it intends to support Icahn's slate but hopes Yahoo hammers out a deal with Microsoft first.

Longtime Yahoo shareholder Ryan Jacob, manager of Jacob Internet fund, also backs the Icahn bid. The best-case scenario, he says, is if Icahn succeeds in ousting Yahoo's current board with a new board more "amenable" to doing a deal with Microsoft.

Icahn's move, in essence, pressures Yahoo to either strike an advertising partnership with Google or merge with Microsoft, tech analysts say.

"Outside of (Yahoo co-founders Jerry) Yang and (David) Filo, most Yahoo shareholders are glad Icahn is forcing the issue," says Jeffrey Lindsay, an analyst at Sanford C. Bernstein.

Icahn's alternate board of 10 nominees is topped by himself and Internet entrepreneur Mark Cuban, who sold Broadcast.com to Yahoo for $6.6 billion in stock in 1999, according to Standard & Poor's Capital IQ. Cuban used part of his Yahoo windfall to buy the NBA's Dallas Mavericks.

"It is unconscionable that you have not allowed your shareholders to choose to accept an offer that represented a 72% premium over Yahoo's closing price of $19.18 on the day before the initial Microsoft offer," Icahn wrote. Yahoo could quickly quash the shareholder mutiny by renewing negotiations with Microsoft, he said.

The investor, who has a colorful history of shaking up corporate boards, has plunked down at least $1.3 billion to gobble up about 59 million Yahoo shares, giving him a roughly 4% stake in the slumping Silicon Valley company.

Yang and the rest of Yahoo's board are under mounting pressure after spurning Microsoft's initial bid of $31 a share, and a sweetened offer of $33 a share.

In a written response late Thursday, Bostock said Icahn's plan "reflects a significant misunderstanding of the facts about the Microsoft proposal" and that Yahoo's board had acted responsibly. Microsoft had no comment.