WILSONVILLE, OR -- A leading Mentor Graphics shareholder today announced it would withdraw its nominees for the board of the EDA software company, choosing instead to support an alternate slate of candidates offered by Carl Icahn.

Casablanca Capital, Mentor's second largest institutional investor with a 5.5% stake, had proposed three individuals for the software firm's board. Likewise, Icahn, who directly or indirectly owns just under 15% of the company, had nominated three candidates of his own.

Icahn also has made a roughly $1.9 billion offer for Mentor, but indicated he would bow out if another bidder emerged.

In an SEC filing, Casablanca said it no longer intended to propose its nominees, stating it wanted “to avoid shareholder confusion that could arise from multiple nominations, and to create the most efficient process for electing nominees to the board.”

In the filing, Casablanca indicated that it was aware of Icahn's slate, but that the two parties are not working together. Mentor has a poison pill in place that goes into effect if a shareholder's position reaches 15%.