In a surprise move, civil rights activist DeRay Mckesson jumped into the crowded contest for Baltimore mayor Wednesday night, shaking up the Democratic field minutes before the deadline to file.

“Baltimore is a city of promise and possibility,” the Black Lives Matter member told The Baltimore Sun. “We can't rely on traditional pathways to politics and the traditional politicians who walk those paths if we want transformational change.”

He said he planned to release a platform within a week. He said it would include a call for internal school system audits to be made public.

Mckesson was the 13th and final candidate to jump into the primary race. In deep-blue Baltimore, the Democratic primary has long determined the winner of the general election.

Mayor Stephanie Rawlings-Blake has declined to run for re-election. Leading candidates include former Mayor Sheila Dixon, state Sen. Catherine E. Pugh, City Councilmen Carl Stokes and Nick J. Mosby, lawyer Elizabeth Embry and businessman David L. Warnock.

Mckesson, 30, a Baltimore native and former public school administrator here and in Minnesota, is part of a team called Campaign Zero, which seeks to end police killings in America. The group wants to end “broken windows” policing, increase community oversight of police and limit use of force, among other goals.

Mckesson has gained widespread attention in the protest movement that began in Ferguson, Mo., and came to Baltimore last year to demonstrate against police brutality after the death of Freddie Gray. He has nearly 300,000 followers on Twitter.

He has met with White House officials and presidential candidates in recent months to discuss civil rights. Former Secretary of State Hillary Clinton has called him a “social media emperor.”

In recent months, Mckesson has been living in North Baltimore.

Dixon, the front-runner in the Democratic primary, said Wednesday she had not heard of Mckesson. She noted there are less than three months to go until the election, and said she wouldn't be distracted.

“We all want the best for Baltimore,” she said. “There are 84 days left. I'm staying focused.”

Recent polls showed Dixon leading the Democratic primary, followed by Pugh and Stokes.

Sean Yoes, the host of the “First Edition” radio show at Morgan State University's WEAA station, said Mckesson's candidacy would “represent a departure from business as usual.”

But he added that Mckesson is likely not well-known among the older African-American women who have long decided Baltimore's elections.

“If the electorate consisted of celebrities who were politically conscious, then maybe he would have a chance,” Yoes said. “I suspect the vast majority of the most prolific voting bloc in Baltimore City do not know who he is. That's going to be problematic for him.”

Later, on the blogging site Medium.com, McKesson contrasted his background with those of the leading candidates. “It is true that I am a non-traditional candidate — I am not a former Mayor, City Councilman, state legislator, philanthropist or the son of a well-connected family. I am an activist, organizer, former teacher, and district administrator that intimately understands how interwoven our challenges and our solutions are,” he wrote.

Johnetta Elzie, another activist with the Black Lives Matter movement, said she was moving to Baltimore to work on Mckesson's campaign.

“I'm definitely going to be on the campaign,” she said. “I'm excited.”

Wednesday was also the deadline to file for Congress. Candidates to succeed retiring Sen. Barbara A. Mikulski include Democratic Reps. Chris Van Hollen and Donna F. Edwards and Republicans Kathy Szeliga, Richard J. Douglas, Chrys Kefalas and Anthony Seda.

In the Baltimore mayor's race, other Democrats running include engineer Calvin Allen Young III, former bank operations manager Patrick Gutierrez, Baltimore police Sgt. Gersham Cupid, author Mack Clifton, former UPS manager Cindy Walsh and nurse Wilton Wilson.

Republican candidates are Armand F. Girard, a retired math teacher; Chancellor Torbit, the brother of a slain police officer; Brian Charles Vaeth, a former city firefighter; Alan Walden, a former WBAL radio anchor; and Larry O. Wardlow Jr., who filed late Wednesday..

The Green Party will hold a primary election between community activist Joshua Harris, Army veteran Emanuel McCray and U.S. Marine David Marriott.

lbroadwater@baltsun.com

twitter.com/lukebroadwater