"Run, Hillary, run," Schumer said at a fundraiser in Iowa Saturday. "If you run, you'll win, and we'll all win."
The third-ranking Senate Democrat promised Clinton his "full and unwavering support," saying her campaign would put to bed the surge of the far-right Republicans that has proved to be a constant thorn in the side of President Barack Obama and Senate leadership.
"With a strong platform and Hillary leading the charge, we will vanquish the Ted Cruz, Tea Party Republicans in 2016 and create a generation of Democrats who will make sure the middle class gets what it needs, our country advances and the torch held by that beautiful lady in New York's harbor burns more brightly than ever."
Schumer supported Clinton in her first presidential bid in 2008, later saying the "time was right for Barack Obama," but "2016 is Hillary's time."
He is one of a growing list of prominent Democrats urging the former Secretary of State to throw her hat in the ring for the next presidential election, a move she has so far declined to make.
Last week, every female Democrat in the Senate signed her name to a letter calling on Clinton to run. House Minority Leader Nancy Pelosi has thrown her support behind Clinton, as have Governors Jay Nixon of Missouri, Mike Beebe of Arkansas, Jennifer Granholm of Michigan and Bill Richardson, former governor of New Mexico, Secretary of Energy and ambassador to the United Nations.
Clinton and her inner circle have repeatedly said she has not made a decision whether to run, but after Schumer's speech Saturday, called his endorsement "very flattering."
"Senator Schumer is an old colleague and an even older friend, and what he said about her is very flattering," said Clinton spokesman Nick Merrill. "Ultimately though, this is a very personal decision that she hasn't made."