(CNN) - Illinois state Sen. Donne Trotter, who was considered by some the frontrunner in the race to succeed U.S. Rep. Jesse Jackson Jr., dropped out Saturday, almost three weeks after prosecutors say he attempted to bring a gun through an airport security checkpoint.
"Today, I formally announce my intention to end my candidacy for that position," the Chicago Democrat told local elected officials, constituents and reporters Saturday in Chicago.
He said he did not intend to make an immediate endorsement, especially as the filing period for the February 26 Democratic primary has not yet begun.
"I know several of the people who are in the race, as I understand it may be 16 or 18" candidates, Trotter said.
But Trotter, who is his party's caucus chairman in the state Senate, said he would be active in the process of electing a successor.
"I do intend to ask the hard questions, demand meaningful answers and do my part in Springfield to help meet the critical needs of the second congressional district," he said. "We need to get to know them better, and we have a short window of opportunity to do that."
Jackson was elected for the 10th time to the U.S. House in November but resigned that month, citing his health. He had been absent from Washington since last spring, and his office said that he was at the Mayo Clinic "receiving intensive medical treatment at a residential treatment facility for a mood disorder."
The FBI and the House Ethics Committee were investigating his financial dealings. In his resignation letter, Jackson wrote, "During my journey I have made my share of mistakes."
"I am aware of the ongoing federal investigation into my activities and I am doing my best to address the situation responsibly, cooperate with my investigators, and accept responsibility for my mistakes, for they are my mistakes and mine alone," he wrote. "None of us is immune from our share of shortcomings or human frailties and I pray that I will be remembered for what I did right."
He is the son of the civil rights leader. Jackson recorded an automated call to voters, but he made no campaign appearances. He was re-elected with 63% of the vote.
Trotter was arrested on December 5 and charged with attempting to bring a handgun and bullets through security at Chicago’s O'Hare Airport, according to CNN affiliates WGN and WLS. The reports said he told police the gun was inadvertently left in his bag after working at his job as a security guard. He is a licensed gun owner and security guard, according to the report.
After his arrest, Trotter initially said he would remain in the race and was among 16 candidates who sought to convince Democratic leaders to select him as the candidate at a party meeting this month.
But no candidate was selected, and instead, there will be an open primary in February. The general election to fill the seat will be on April 9. Candidates can file for the primary between January 3 and 7.
Trotter has served in the state Senate since 1993, and before that served in the state House.
– CNN's Alan Duke and Dana Davidsen contributed to this report.