(SOUNDBITE) (English) DEMOCRATIC PRESIDENTIAL CANDIDATE BERNIE SANDERS, SAYING: "Hi, I'm Bernie Sanders and I'm running for president." Bernie Sanders is making his second run for presidency.

The Vermont Senator, an independent, made the announcement Tuesday - saying his 2020 campaign is part of a larger movement.

(SOUNDBITE) (English) DEMOCRATIC PRESIDENTIAL CANDIDATE BERNIE SANDERS, SAYING: "Our campaign is not only about defeating Donald Trump…Our campaign is about transforming our country and creating a government based on the principles of economic, social, racial and environmental justice." The 77-year-old vowed to finish what he started in 2016 when he failed to beat Hillary Clinton for the Democratic nomination.

But Sanders is entering a very different race this time around.

First of all, it's much more crowded.

He faces a field populated with progressive liberals, like Elizabeth Warren, touting some of the same ideas he brought into the mainstream.

Also, he won't be an underdog.

Sanders has been among the leaders in opinion polls among 2020 candidates.

A much different scenario than the start of his long-shot bid in 2016 when he ran against Hillary Clinton.

But this race, won't come without challenges.

Sanders is likely to face questions about his age and relevance in a party increasingly advancing more diverse and fresh voices.

Including those of women and minorities - groups Sanders struggled to win over in 2016.