Dan Pfeiffer, one of President Obama's longest-serving aides, will step down from the White House as soon as the end of the month. Pfeiffer served with Obama since the early days of his first presidential campaign, ultimately rising to become his senior adviser.
"Dan has been beside me every step of this incredible journey," Obama said in a statement, adding, "and through it all he's been smart, steady, tireless and true to the values we started with."