Nancy Pelosi 'Proud to Endorse' Hillary Clinton for President

— -- House Minority Leader Nancy Pelosi endorsed Hillary Clinton for president this morning on "Good Morning America" before her home state's primary today.

"I'm a voter in California and I have voted for Hillary Clinton for president of the United States and proud to endorse her for that position," the Democratic superdelegate said, though adding "it's not over until it's over."

Pelosi, who did not formally endorse in the 2008 Democratic primary, has praised Sen. Bernie Sanders' primary campaign and the excitement the Vermont senator has generated among younger voters.

In an interview with ABC News’ George Stephanopoulos today, Pelosi said she believes Sanders will be a constructive force before the Democratic convention in Philadelphia.

"Bernie knows better than anyone what's on the line in the election and that we at some point have to unify as we go forward," she said. "He wants to influence the platform. I think that’s fine."

Pelosi also responded to a question about the prospect of Massachusetts Sen. Elizabeth Warren's joining the Clinton ticket.

"We've had two men over and over again for hundreds of years," she told Stephanopoulos. "I think that two women, whoever they may be, that would be fabulous as well, but Hillary Clinton will choose the person that she feels most comfortable with."

And while it's "exciting" to see the first female nominee for a major party, Pelosi said, Clinton's historic achievement is "because she is the best, not because she's a woman."

ABC News estimates that Hillary Clinton secured enough delegates to clinch the Democratic nomination for president Monday night, based on new Associated Press counting of superdelegate endorsements, making Clinton the first woman to clinch a major party's presidential nomination.

Eight years ago, Clinton ended her first primary campaign for president and endorsed then-Senator Barack Obama.