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On Saturday, the Egyptian Muslim Brotherhood (MB) announced the nomination of Deputy Supreme Guide Khairat al-Shater for president, cementing a critical shift in its political strategy. Although the group initially tried to manage Egypt's post-Mubarak transition by cooperating with the Supreme Council of the Armed Forces (SCAF) and secularist parties, it is now pursuing outright political dominance. The MB's reversal of its oft-repeated pledge not to run a presidential candidate also suggests that it cannot be trusted if it decides there is an advantage to be won. More broadly, the Brotherhood's pursuit of a political monopoly undermines prospects for democracy in Egypt and threatens to intensify political instability -- a scenario that should deeply alarm U.S....