Elizabeth Warren will declare her Senate candidacy Wednesday, a source close to the Harvard Law School professor and a Massachusetts Democratic Party official confirmed to Roll Call.

Warren will greet commuters in Boston in the morning and then travel to the cities of New Bedford, Framingham, Worcester and Springfield.

Warren has been making moves toward a bid for the seat now held by Sen. Scott Brown (R) for weeks and recently formed an exploratory committee. She has been making her way around Massachusetts and introducing herself to voters at house parties, mostly with friendly crowds, in recent weeks.

Some Democrats in the Bay State have worried how effective a candidate the consumer advocate and professor at Harvard Law School will be. Warren is a political novice and is untested in the rigors of a hard-fought federal campaign with national interest in the outcome.

But she has been working to assuage any doubts about her among Democrats in recent days, giving an impassioned defense of the middle class to a group of key politicians, union leaders and activists on Labor Day. Chosen to be the keynote speaker for the Greater Boston Labor Council’s yearly breakfast, she received an exceedingly warm response from the influential crowd.

Warren will face a handful of candidates in the Democratic primary, but she is expected to significantly outraise all of them and have the support of much of the Massachusetts Democratic establishment. If she wins the primary, her fight with the well-liked junior Senator from Massachusetts will be a tougher battle.

Roll Call rates the race as a Tossup.