This is government of the few, by the few and for the few. pic.twitter.com/5fuCwP1VRo — Bernie Sanders (@SenSanders) April 28, 2015

He will become the second Democratic presidential candidate to declare, following Hillary Clinton, with whom he is sure to grapple in an ideological struggle.

Sen. Bernie Sanders is gearing up to launch a presidential campaign as a Democrat Thursday, a source familiar with the campaign confirmed to msnbc.

The Vermont senator has said he will make a decision on a presidential run by the end of the month, and has been leaning strongly towards “yes” in recent days. The senator has been openly and actively considering a bid for months, visiting early presidential primary states to asses whether his run would be viable.

At a town hall meeting with students at Howard University Tuesday evening, Sanders was asked if it was true he planned announce his candidacy Thursday, and how young people can get involved. “Let me be diplomatic,” Sanders replied. “I promised I would make a decision by the end of this month. Today is, what the 28th? A formal decision will be announced before the end of this month. And we would love to have your help.”

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“I think we’re coming to the critical moment of truth here. He’s now spent enough time traveling around the country talking to people and feels there is genuinely a large audience of people who are with him,” veteran Democratic strategist Tad Devine, who is advising Sanders, told msnbc last week.

Sanders’ Thursday announcement will be low-key – likely just a short written statement. A formal kick-off rally will come later in May in Burlington, where Sanders served as mayor.

Vermont Public Radio first reported Sanders’ decision to announce Thursday, citing several sources familiar with the senator’s deliberations.

Sanders is an Independent who caucuses with Democrats in the Senate, and plans to run for president as a Democrat. He identifies as a social Democrat, and sits proudly on the left flank of the party. While he has valued his independent status for decades in Vermont, the senator wants to be on the Democratic debate stage and sees a more clear path to potential victory inside the party.

But Sanders may not need to formally change his party affiliation, since there is no party registration in Vermont.