Boston City Councilor Tito Jackson offered a preview of his mayoral candidacy at a campaign kickoff in Roxbury on Thursday, mixing lofty, occasionally theological rhetoric with sharp jabs at the track record of incumbent Mayor Marty Walsh.

Jackson began his speech by invoking the concept of grace, saying he’s been a recipient throughout his life — ever since he was born at the old Boston City Hospital to a 13-year-old sexual assault victim who gave him up for adoption.

“Grace, for those who are into it, is a common noun that has an uncommon and very personal definition for me,” Jackson told the audience at Haley House, a Roxbury restaurant known for hiring formerly incarcerated people. “According to Merriam-Webster’s Dictionary, it means ‘unmerited divine assistance given humans for their regeneration.’”

After urging the crowd to respond — “Can a brother get an amen?” — Jackson continued: “For me, grace represents my start, is my present, and will be my end.”

Jackson painted a rosy picture of his childhood in Roxbury but drew a sharp contrast with the Boston of 2017. Today, he suggested, Boston has lost its moral compass, providing tax breaks to rich, out-of-town companies like General Electric while middle- and working-class families struggle to find affordable housing and public schools go underfunded.

“Boston is at a crossroads,” Jackson said. “We’re at a fork in the road, a decision point. The middle class in our beloved community and the neighborhood I grew up in stands in the balance.”

Walsh was at Boston Police Headquarters in Roxbury, which sits less than half a mile from Haley House, on Thursday afternoon to announce a new collaboration between the BPD and Big Brothers Big Sisters — his first public appearance since Jackson announced his challenge Wednesday night.

“I respect the councilor, and, you know, he’s done some great work as a member of the Council,” Walsh said.

Walsh has spoke to Jackson about the race, he said, and asked his challenger to “keep this race clean.” He also noted that Mary Franklin — an anti-violence activist who’s considered a far less serious challenger than Jackson — plans to run as well.

The challenges facing Jackson are significant. While Marty Walsh has well over $3 million in his campaign war chest, Jackson has less than $100,000. But Jackson struck a confident note Thursday, saying of his candidacy: “My time will come and has come.”

A win would make Jackson Boston’s first African-American mayor and the first challenger to unseat an incumbent since 1949, when John Hynes defeated James Michael Curley.