Clinton has been careful to remain close to key Democratic voters, speaking before students, black women and the gay and lesbian community in recent months. While she has given speeches around the country, she has not visited the early voting state of Iowa.
Many top Democrats have been urging Clinton to run. The Ready for Hillary super PAC, launched by her supporters, has received endorsements from Democrats such as Sen. Claire McCaskill of Missouri and former Michigan Gov. Jennifer Granholm.
Other potential Democratic candidates seeking the 2016 nomination include Vice President Joe Biden, New York Gov. Andrew Cuomo and Maryland Gov. Martin O'Malley.
Iowa state Sen. Liz Mathis, a Democrat from Robins, said she was excited by Schumer's announcement.
"It paves a way into her election," said Mathis, who was a caucus leader for Clinton in 2008. "Primarily women in the party have come out in support of her, so it's very good to see male leaders in the party, too. It's important that everyone in the Democratic Party come out."
Associated Press writer Ken Thomas in Washington contributed to this report.