By Chris Casteel Washington Bureau ccasteel@oklahoman.comPHILADELPHIA — U.S. Sen. Bernie Sanders sought to quell an uprising of his supporters Monday, telling them that it was important to unite behind Democrat Hillary Clinton. Addressing the legion that made up his political revolution, Sanders said no one was more disappointed than he was that he didn't win the Democratic presidential nomination. But given the contrast between Clinton and GOP presidential candidate Donald Trump, Sanders said, “Hillary Clinton must become the next president of the United States.” Sanders, 74, whose populist campaign pulled upsets in several states and drew millions of people into the political process, frustrated some Democrats in continuing his campaign long after Clinton had clinched the nomination. But he endorsed her earlier this month and has been unwavering since.Read more on NewsOK.com