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Some Democrats are calling for Defense Secretary Donald Rumsfeld (search) to resign amid controversy surrounding pictures depicting U.S. military personnel abusing Iraqi prisoners outside of Baghdad.

But others say the demand for pink slips is merely politics in an election year when Democrats are hoping to oust President Bush.

"The Congress will politicize this, will spend too much time investigating it," Sen. Joe Lieberman, D-Conn., told Fox News. "The other danger is, the administration will be defensive about this instead of being aggressive ... This has been a setback for our cause."

Although Rumsfeld was scheduled to testify before House and Senate lawmakers Friday on what he knew and when he knew it, Democrats, whose relations with the defense secretary have long been strained, said more than that was required.

• Raw Data: Articles of Impeachment for Rumsfeld Entered by Rep. Rangel (pdf)

"The Pentagon (that) Secretary Rumsfeld oversees has become an island of unaccountability, ignoring the Geneva Conventions, our allies and common sense," House Democratic leader Nancy Pelosi of California said Thursday.

Sen. John Kerry, battling Bush for the White House, pushed for Rumsfeld's ouster.

"It's the way it was handled," Kerry said on a campaign stop in California. "The lack of information to the Congress, the lack of information to the country, not managing it, not dealing with it, recognizing it as an issue."

Rep. Charles Rangel, D-N.Y., said Congress should impeach Rumsfeld if he declines to resign and the president refuses to fire him. The New York Times seconded those demands with a Friday editorial headlined, "Donald Rumsfeld Should Go."

With both houses of Congress under Republican control, impeachment wasn't on the agenda. Bush himself has said Rumsfeld has a job so long as he's in the White House.

He "is a really good secretary of defense. Secretary Rumsfeld has served our nation well. Secretary Rumsfeld has been the secretary during two wars," Bush said Thursday. "He's an important part of my Cabinet and he'll stay in my Cabinet."

At the same time, Bush confirmed for reporters that he had expressed his unhappiness with his defense secretary privately earlier in the week. He said he told Rumsfeld that "I should have known about the pictures and the report" done by the Pentagon before they turned up in news reports.

Lieberman told Fox News that the calls for Rumsfeld's ouster are a distraction from the larger picture.

"We're in the middle of a war — you wouldn't want to have the secretary of defense change unless there's really good reason for it and I don't see any good reason at this time," Lieberman said.

But the senator said it's imperative to get to the bottom of what happened as soon as possible.

"Let's flush it all out, clean it up and get back to the war on terrorism," Lieberman continued.

Some Republicans hastened to accuse Democrats of playing politics with the issue.

"They want to win the White House more than they win the war (on terror) and our enemies know it," said House Majority Leader Tom DeLay, R-Texas.

Former House speaker and Fox News political analyst Newt Gingrich (search) said Rumsfeld is more than able to continue in his position, pointing out on Friday that the defense secretary has been leading the war effort in this country for three years while making huge strides in transforming the Pentagon.

Pelosi's and others' calls for a resignation are "a sign that opportunism always seeks an occasion in Washington," he said.

"There's zero reason for Donald Rumsfeld to resign and every reason for the president and Donald Rumsfeld to tell the truth," Gingrich said. "It's just politics in a presidential election."

"The only call that really matters is the one the president makes, and he has expressed full confidence in Secretary Rumsfeld," Deputy Secretary of State Richard Armitage said in a television interview. "We've got a war going on. He's been a fine secretary, and I think we'll let it rest at that."

Joe Allbaugh, former director of the Federal Emergency Management Agency (search) and Bush-Cheney campaign director, agreed that Democrats can complain all they want but what matters in the end is what the commander in chief wants.

The criticism of Rumsfeld "is just a continuation of what started when he, three-and-a-half years ago, wanted to modernize the Defense Department," Allbaugh told Fox News. "It's going to pile on but it's not going to make a difference. The president makes a difference."

Fox News' Liza Porteus and The Associated Press contributed to this report.