(CNN) Former Democratic hopeful Marianne Williamson made a surprise appearance at Sen. Bernie Sanders' rally Sunday in Austin, Texas, to announce her endorsement of the Democratic front-runner.

"Bernie Sanders has taken a stand, and Bernie Sanders has been taking a stand for a very long time. He has been consistent, he has been convicted, he has been committed. And now it's time, I'm here and you're here, because it's time for us to take a stand with Bernie," Williamson told the crowd in Austin.

Williamson dropped out of the Democratic race on January 10. She had endorsed Sanders in his first presidential run in May 2015.

On Sunday, she argued that Sanders is proving the Democratic establishment wrong.

"We're being told oh, it can't happen. He can't beat (President Donald) Trump. Bernie can't beat Trump, it can't happen," Williamson said. "I'll tell you what's already happened to those who say it cannot happen. You just tell them this. It already happened. He won Iowa. It already happened, he won New Hampshire. It already happened, he won Nevada," Williamson added, pointing to Sanders' growing momentum.

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