When President Barack Obama appears at the Port of New Orleans tomorrow, he won't be joined by Louisiana's only statewide elected Democrat, U.S. Sen. Mary Landrieu. Landrieu will travel with Obama to New Orleans on the president's plane, Air Force One, but she doesn't plan to attend his speech about boosting exports. The U.S. Senator has a long-standing engagement in Lake Charles that takes place at the same time and she can't be in both places at once, staff said. Her absence at Obama's public appearance in Louisiana this year could raise some questions. Landrieu is expected to face a...