A prominent Black Lives Matter activist has made a late entry into the Democratic race for Baltimore mayor. 

DeRay Mckesson filed to run Wednesday, the deadline for candidates in Maryland's April 26 primary. He joins a dozen contenders, including former Mayor Sheila Dixon, who will seek to succeed Stephanie Rawlings-Blake.

In Baltimore, as in other heavily Democratic cities, the primary has long determined the general election winner. The city has not had a Republican mayor since Theordore McKeldin, who served from 1963 to 1967.

Rawlings-Blake opted not to run after last year's unrest over the death of Freddie Gray in police custody, saying she wanted to focus on seeing the city through the trials of six officers charged in the case.

Mckesson, a Baltimore native, has been a prominent figure in protests over Gray's case, as well as the August 2014 death of Michael Brown in Ferguson, Mo.

Mckesson told The Baltimore Sun that he expects to release a platform within a week, and acknowledged that his late entry into the race would mean he'd have some catching up to do.

"We can't rely on traditional pathways to politics and the traditional politicians who walk those paths if we want transformational change," he told the paper.

Mckesson's prominence in the Black Lives Matter movement has made him a sought-after endorsement in this year's race for the Democratic presidential nomination. He has met with both Hillary Clinton and Sen. Bernie Sanders, as well as White House Senior Adviser Valerie Jarrett. 

The Associated Press contributed to this report.