"I'm not shy, and I'm not retiring," said Mikulski, a Democrat and the senior female senator, in an interview. "I've suited up, and I'm healthy and I'm pumped up."
Mikulski officially launched her campaign with a morning event at Jimmy's Restaurant in Fells Point, a longtime Baltimore political hangout. She had acknowledged weeks ago that she would seek re-election despite rumors that she might be considering retirement.
"I want to keep on fighting" for constituents, she said. "I want to keep on being a reformer, fighting for health care reform and getting rid of punitive practices of insurance companies."
Mikulski, 73, is seeking re-election at a time when anti-incumbent sentiment is running high nationally. But she said Maryland is running against that trend.
"I don't think it is ‘anti-incumbent' as much as an ‘anti-do nothing,'" she said. "They know that I'm a fighter, I'm a doer. They know it is what I'm going to keep on doing."
She consistently ranks as one of the most popular politicians in Maryland and is an energetic campaigner and effective stump speaker. Having her at the top of the ticket could help other more-vulnerable Democrats seeking office this year, such as Gov. Martin O'Malley and Rep. Frank Kratovil of the 1st District.
Mikulski had $2.7 million in available campaign cash as of the most recent reporting period, records show.
Among the Republicans seeking the nomination: Eric Wargotz, a physician and Queen Anne's County commissioner, had $112,000 available, after loaning himself $75,000; and James B. Rutledge III, a Harford County lawyer, had $4,000 available (after giving his campaign a $25,000 personal loan.)
Mikulski planned to follow Friday's announcement with a statewide tour running through Sunday.