Story highlights House Minority Leader Nancy Pelosi endorsed Hillary Clinton on Tuesday morning

Pelosi was one of just a handful of prominent Democrats who declined to endorse Clinton during the primary battle

Washington (CNN) The House's top Democrat, Minority Leader Nancy Pelosi, endorsed Hillary Clinton Tuesday, shortly after Clinton locked up the Democratic nomination and as voters head to the polls in Pelosi's home state.

"I'm a voter in California and I have voted for Hillary Clinton for president of the United States and I'm proud to endorse her for that position. But I hasten to say that it's not over until it's over," Pelosi, who represents San Francisco in Congress, told ABC's "Good Morning America."

CNN called the Democratic race for Clinton Monday after determining that Clinton had secured enough superdelegates to win the Democratic nomination next month. Clinton herself hesitated to declare victory just yet, looking for a strong final showing in California and the other states voting Tuesday.

Pelosi was one of just a handful of prominent Democrats who declined to endorse Clinton during the primary battle -- saying as recently as a few days ago that she was not ready to endorse -- although she often praised Clinton throughout the campaign and was expected to endorse her. President Barack Obama is expected to endorse Clinton this week as party leaders look to unify against presumptive Republican nominee Donald Trump ahead of the November general election.

Sanders refused to concede Monday night, with a sharp statement from his campaign saying he was not leaving yet. Pelosi said Tuesday she understood why Sanders was staying in and fighting.

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