"It's not about this election. It's about the next generation," Cardin said from a pier near the Baltimore Museum of Industry.
tea party politicians and what he called their attempts to "turn back" social programs, women's rights and civil rights.
Supporter Helen Stith-Smith, 66, cheered on Cardin for his near-15-minute speech. He was joined by most of the state's Democratic leaders, including Gov. Martin O'Malley, U.S. Sen. Barbara A. Mikulski and Baltimore Mayor Stephanie Rawlings-Blake.
"He's done the right thing for us," the Pikesville resident said while holding a campaign sign. "He has been there for us. I love him and will support him any way I can."
In Congress, Cardin, 68, has established himself as a leader on fiscal and environmental issues.
He appears well positioned to win a second term. He has been raising cash at a solid clip and has more than $2.3 million in the bank, Federal Election Commission reports show.
Cardin may face a challenge in the April 3 primary from state Sen. C. Anthony Muse of Prince George's County. On the Republican side, the candidate who appears to be campaigning most aggressively is former U.S. Secret Service agent Daniel Bongino of Severna Park.
Bongino welcomed Cardin to the race, saying he looked forward to an issues-based campaign. "Marylanders are eager to turn the page on status quo politics," Bongino said.
Before Cardin's 2006 election to the Senate to succeed Paul Sarbanes, he served in the House of Representatives for 20 years. He also had a long run in the Maryland General Assembly, where he was speaker of the House of Delegates.