It's not often that President Bush, who casts himself as decisive and bold, is cut off from decisions of grave importance to his presidency.

But as he and his team brace for the results of a lengthy CIA leak investigation that has reached inside his famously cloistered White House, threatening to topple his senior aides and tarnish his image, Bush is watching, powerless, from the sidelines.

The immediate risks for the president are clear: the possible indictment of Karl Rove, one of his closest and most influential advisers; I. Lewis "Scooter" Libby, Vice President Dick Cheney's powerful chief of staff; or others in his administration. What might be harder to measure is the effect on Bush and his presidency of such blows, which could come during the next two weeks, when Patrick J. Fitzgerald, the federal prosecutor leading the probe of how a covert CIA agent's identity was revealed, is expected to wrap up his two-year investigation.

The stepped-up pace of Fitzgerald's work in recent weeks suggests that "he's coming to closure," said Stephen Gillers, a New York University law professor. And the prosecutor's intensifying focus on Rove, who gave his fourth round of grand jury testimony Friday, suggests that Bush's valued aide "is in harm's way."

"The White House can only hold its breath and pray," Gillers said.

A Rove indictment would shake the White House and damage Bush at a time of intense difficulty, robbing the president of the strategist he has relied on since his earliest days in politics, and tainting Bush and the rest of his inner circle by association.

"It's basically the figurative end of the Bush administration," said Paul C. Light, a New York University public service professor who specializes in the federal bureaucracy.

"They're already teetering on lame-duck status," Light said, because of the outcry over Bush's response to Hurricane Katrina, his choice of White House counsel Harriet E. Miers for the Supreme Court, and Republican leaders in the House and Senate under investigation.

Add an indictment, he added, and, "For all intents and purposes, you have an administration frozen in time for the next three years - it just couldn't be worse for them."

Losing Libby would likely create fewer ripple effects for Bush, but it would nonetheless reflect poorly on his administration, which initially claimed to have had no involvement whatever in outing Valerie Plame, a CIA operative whose husband, former Ambassador Joseph C. Wilson IV, sought to discredit Bush's case for the war in Iraq.

Fitzgerald's probe has rattled the Bush White House, throwing off-balance a team known for steadiness in tumultuous times, and adding unpredictability for aides who prefer sticking to a meticulously crafted script.

The White House argued Friday that Bush and his staff aren't sidetracked by the investigation, saying the president is focused instead on priorities such as the outcome of the Iraqi constitutional referendum, helping the victims of Hurricane Katrina and addressing high gas prices.

"While there are other things going on, the White House doesn't have time to let those things distract from the important work at hand," Bush spokesman Scott McClellan said just after Rove completed what his lawyer, Robert D. Luskin, said would be his final round of grand jury testimony.

Rove's multiple appearances have fueled speculation that he could be indicted, but Luskin said Friday that Rove hasn't been told he's a target of the probe.

Still, the investigation transcends the typical Washington scandal sideshow because it goes to the heart of Bush's most important decision as president: the war in Iraq. A key question for Fitzgerald has been whether White House aides exposed Plame to retaliate against her husband for writing a July 2003 op-ed piece in The New York Times contending that Bush twisted intelligence to strengthen his case for the war.

The prosecutor's work has shone a spotlight on a standard - but nonetheless unseemly - practice that politicians and operatives prefer to keep hidden: the hardball tactics used by presidents to smear their critics.

McClellan, in his first public comments about the leak investigation in July 2003, said, "That is not the way this president or this White House operates." But subsequent accounts by journalists who spoke to Rove and Libby indicate just the opposite, suggesting the two might have led a quiet White House effort to discredit Wilson's assertions about Iraq.

Fitzgerald's hunt has thus created a public-relations debacle for the White House, which has moved from categorical denials that Bush's aides had anything to do with the leak, to more measured statements by Bush promising to oust anyone indicted for a crime, to flat refusals to comment on a continuing investigation that appears closer by the day to snaring top aides.

Rove, 54, who spent 4 1/2 hours at a federal courthouse Friday, is at the center of the maelstrom. A college dropout gifted in politics and policy, Rove has been Bush's tutor and top strategist on both for three decades, making him as indispensable as he is fiercely loyal to the president.