In a debate that covered war in Iraq, statehood for the District of Columbia and the health of the Chesapeake Bay, Sen. Barbara A. Mikulski (D) defended her record against criticism from Republican challenger state Sen. E.J. Pipkin (Queen Anne's).

The two sat side by side yesterday at the WTOP radio studio in Northwest Washington and faced off for an hour in their second and final scheduled discussion before the Nov. 2 election.

For the most part, their stances were predictable: Pipkin, a conservative, attacked the liberal Mikulski for voting more than 350 times to raise taxes; she called the charge a "cookie-cutter" GOP tactic. Pipkin said he would be more friendly to small businesses; Mikulski dwelt on what she has done and will do to promote jobs.

On the environment, however, the discussion took an unexpected turn.

Pipkin, 47, a relative newcomer to politics, focused in part on the issue that brought him to prominence -- a 1999 plan by then-Gov. Parris N. Glendening (D) to dump dredge spoils in the bay. Pipkin led a campaign of opposition, which helped kill the plan. He accused Mikulski of inaction.

To bolster his case against Mikulski, he cited a letter Rep. Wayne T. Gilchrest (R-Md.) wrote him. "[E]ven at the height of our fight, when every Democrat in the Maryland Congressional delegation refused to help stop the dumping, you did not back down," Gilchrest wrote Oct. 10.

Mikulski unsheathed her own missive -- an Oct. 13 letter of endorsement from Betsy Johnson, chairman of the Sierra Club's Maryland chapter: "[Y]ou kept a keen eye on the proposed open water placement of dredge material. . . . You and your staff met with numerous citizens, including Mr. Pipkin . . . "

"I'm true green, I'm not pale green," said Mikulski, who has received higher ratings from environmental watchdog groups than Pipkin has received.

Pipkin later backed off the letter tactic, asking listeners to take a broad view. "You just have to ask a couple of common-sense questions," he said. "Since Ms. Mikulski's been in Washington, what's happened to the bay? Fewer crabs, fewer oysters, fewer bay grasses. . . . While Ms. Mikulski likes to wave letters around from various groups, the bay continues to slip away."

Pipkin began the debate by citing a letter Mikulski and other senators wrote in 1998, urging then-President Bill Clinton "to take necessary actions . . . to respond effectively to the threat posed by Iraq's refusal to end its weapons of mass destruction programs," and suggesting that her 2002 vote against the use of force against Iraq was inconsistent with her earlier view. Mikulski countered that she had supported the Bush administration's use of force in Afghanistan and that she had made the "global war against terrorism" her priority.

Pipkin disputed Mikulski's assertion that he had engaged in a series of personal attacks against her. "The first sign that an incumbent has stayed in office too long is when a commercial about their record is taken as personal attack," he said. In advertising and in their first debate, Mikulski has questioned Pipkin's background, saying his work with junk bonds on Wall Street made him part of a "culture of corporate raiders."

He has defended junk bonds as a legitimate means of raising capital.

The two candidates were questioned by Washington Post deputy editorial page editor Colbert I. King and WTOP political commentator Mark Plotkin, who has long promoted District voting rights.

Both candidates said they supported a bill proposed by Rep. Thomas M. Davis III (R-Va.) that would give the District a single vote in the House of Representatives; Pipkin did not share Mikulski's support for full representation in both houses of Congress.

Sen. Barbara A. Mikulski responded to verbal jabs from state Sen. E.J. Pipkin, describing her environmental stance as "true green, I'm not pale green."