A lawsuit brought by a CIA agent whose cover was blown by Bush administration officials, Valerie Plame, is expected to face a withering attack this morning at a court hearing in Washington.

Through their attorneys, the defendants in the case have denounced it as a political vendetta on the part of Ms. Plame and her husband, Joseph Wilson, a former ambassador. Named in the lawsuit are Vice President Cheney, his former chief of staff, I. Lewis Libby Jr., President Bush’s top political adviser, Karl Rove, and a former deputy secretary of state, Richard Armitage.

“This case is a political exercise masquerading as a civil lawsuit,” Mr. Armitage’s lawyers complained in their motion to dismiss the case. Judge John Bates is scheduled to hear two hours of arguments today on whether the suit should go forward. The federal government, which was not named as a defendant, has also urged that the case be thrown out.

The lawsuit alleges a plot among government officials to expose Ms. Plame’s CIA affiliation as retribution for her husband’s criticism of claims Mr. Bush used to justify the invasion of Iraq. In particular, the suit claims that the defendants violated Mr. Wilson’s right to freedom of speech, violated the couple’s rights to equal protection under the law, violated Ms. Plame’s constitutional right to privacy, and deprived Ms. Plame of her property interest in continuing employment at the CIA. The suit also alleges that the defendants committed a tort against her by disclosing “private facts,” namely her classified affiliation with the agency.

The suit faces a formidable array of legal hurdles that could lead to its dismissal. The defendants argue that the legal theories underpinning the case are invalid, that Mr. Cheney is immune from lawsuits relating to his duties, and that the other defendants are immune because the type of wrongdoing alleged by the couple has never been “clearly established.”

In addition, the defendants claim that allowing the suit to proceed would result in the disclosure of classified information about Ms. Plame’s duties and those of other CIA employees. “For the defendants to now say that they cannot be held liable because the information is secret and sensitive is much like the child who kills his parents and begs for mercy on the grounds that he is an orphan,” the couple’s attorneys wrote.

The briefs in the case were filed before a jury convicted Libby of obstruction of justice and perjury charges in March. “I think the criminal trial proves pretty conclusively that you can go forward with litigation of this kind and really not have any risk at all to national security,” a lawyer for the couple, Anne Weisman, said.

An attorney for Libby, Alex Bourelly, noted that the criminal charges against Libby did not relate to the leak, but to whether he had been honest with the FBI. The trial also skirted the issue of Ms. Plame’s duties at the CIA. “In the criminal case, we weren’t allowed discovery into a great many areas, notably what her status actually was,” he said. “No jury was asked to assess any of that.”

The couple may face an uphill battle to win over Judge Bates. He was appointed by Mr. Bush in 2001 and once served as a deputy to an independent counsel who investigated President Clinton, Kenneth Starr.