WASHINGTON—Like twin Jacques Cousteaus of the political world, President Bush and Congress are probing the depths of public opinion polling as voters exasperated over Iraq, immigration, and other issues give them strikingly low grades.

In a remarkable span, the approval that people voice for the job Mr. Bush is doing has sunk to record lows for his presidency in the AP-Ipsos and other polls in recent weeks, dipping within sight of President Nixon’s levels during Watergate. Ominously for Republicans hoping to hold the White House and recapture Congress next year, Mr. Bush’s support has plunged among core GOP groups like evangelicals, and pivotal independent swing voters.

Congress is doing about the same. Like Mr. Bush, lawmakers are winning approval by roughly three in 10. Such levels are significantly low for a president, and poor but less unusual for Congress.

“The big thing would be the war,” said independent Richard MacDonald, 56, a retired printer from Redding, Calif. “I don’t think he knew what he got into when he got into it.” As for Congress, Mr. MacDonald said, “It’s just the same old same old with me. A lot of promises they don’t keep.”

Mr. Bush was risking more unpopularity by commuting I. Lewis “Scooter” Libby’s prison term in the CIA leak case, and his refusal to rule out a full pardon. Polls in March after the former White House aide’s conviction showed two in three opposed to a pardon. The public’s dissatisfaction may be more serious for Republicans because even though Mr. Bush cannot run again, he is the face of the GOP. He will remain that until his party picks its 2008 presidential nominee — and through the campaign if Democrats can keep him front and center.

“Everything about this race will be about George Bush and the mess he left,” Rep. Rahm Emanuel, a Democrat of Illinois and a member of the House Democratic leadership, said about 2008. “He’ll be on the ballot.”

Congress’s numbers could signal danger for majority Democrats, since they echo the low ratings just before the GOP 1994 takeover of the House and Senate, and the Democratic capture of both chambers last November.

But unlike the president, Congress usually has low approval ratings no matter which party is in control, and poor poll numbers have not always meant the majority party suffered on Election Day. Voters usually show more disdain for Congress as an institution than for their own representative — whom they pick.

A majority in a CNN-Opinion Research Corp. survey in late June said Democratic control of Congress was good for the country. Yet only 42% approved of what Democratic leaders have done this year — when Democrats failed to force Mr. Bush to change policy on Iraq. Republican strategists hope the dim mood will help the GOP in congressional elections.

“The voters voted for change and they expected change, and they see an institution still incapable of getting anything done,” said GOP pollster Linda DiVall.

The abysmal numbers are already affecting how Bush and Congress are governing and candidates’ positioning for 2008.

Last Thursday’s Senate collapse of Mr. Bush’s immigration bill showed anew how lawmakers feel free to ignore his agenda. Senators Lugar of Indiana and Voinovich of Ohio, both Republicans, have joined increasingly bipartisan calls for an Iraq troop withdrawal.

This year’s GOP presidential debates have seen Mayor Giuliani, Senator McCain of Arizona, and others criticize Mr. Bush or his administration for mishandling the war and other issues. Some Republican congressional candidates have not hesitated to distance themselves from Mr. Bush.

“President Bush is my friend, and I don’t always agree with my friends,” said Senator Smith, a Republican of Oregon, facing a tough re-election fight next year. “And on the issues of Iraq and immigration, I simply disagree with his approach.” Mr. Bush’s doleful numbers speak for themselves. In an early June AP-Ipsos poll, 32% approved of his work, tying his low in that survey. Other June polls in which he set or tied his personal worst included 27% by CBS News, 31% by Fox News-Opinion Dynamics, 32% by CNN-Opinion Research Corp., and 26% by Newsweek. The Gallup poll’s lowest presidential approval rating was President Truman’s 23% in 1951 and 1952 during the Korean war, compared with Nixon’s 24% days before he resigned in August 1974. Mr. Bush notched the best ever, 90% days after the attacks of September 11, 2001.

The AP’s June survey showed that compared with an AP exit poll of voters in November 2004, Mr. Bush’s approval was down among swing voters. His support dropped from about half of independents to a fifth; from half to a third of Catholics, and from nearly half to a fifth of moderates. Among usually loyal GOP voters, his approval was down from about eight in 10 to roughly half of both conservatives and white evangelicals.

Congress had a 35% approval rating in a May AP-Ipsos survey. Polls in June found 27% approval by CBS News, 25% by Newsweek and 24% by Gallup-USA Today. Congress’s all-time Gallup low was 18% during a 1992 scandal over House post office transactions; its high was 84% just after September 11.

In the AP poll, lawmakers won approval from only about three in 10 Midwesterners, independents and married people with children — pivotal groups both parties court aggressively.