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President Bush campaigned Thursday for a congressman who has confessed to adultery and a senator accused of racial insensitivity, seeking to boost incumbent Republicans once safe for re-election but now in peril.

Bush's appearances for Rep. Don Sherwood here and for Sen. George Allen in Richmond, Va., found the White House on the defensive over the decision to try to help candidates in such straits as the GOP struggles to keep control of Congress.

"I think the president understands that it's important to set high standards," said spokesman Tony Snow.

Bush, whose low approval ratings and identification with the unpopular war in Iraq has caused some Republicans to see him as a liability, tried to keep the focus on his contentions that Democrats would go soft on the war on terror and raise taxes if handed a majority in the November elections.

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But the pictures of the day were of Bush descending from Air Force One in Pennsylvania alongside Sherwood, his wife and one of their daughters, who were secreted onto the plane to set up the photo-op, and of the grinning foursome's appearance later at a local farmer's ice cream store.

Allen opted for a slightly less robust presidential embrace, merely greeting Bush at the bottom of his airplane's stairs and keeping a bit of a distance on their pumpkin-buying stop at a roadside stand. Sticking closely by Allen's side throughout was state Sen. Benjamin Lambert, who is black and a Democrat who has endorsed the GOP senator.

Sherwood has held one of the safest seats in Congress, his conservatism playing well in his heavily Republican, rural district in northeastern Pennsylvania. Democrats didn't even bother fielding a candidate in the past two elections. But last year, Sherwood admitted to a five-year extramarital affair with a woman 35 years his junior. He settled a lawsuit that claimed he had choked her — he has denied he abused her — and has aired a campaign commercial asking constituents to forgive his infidelity.

Helping to raise more than $300,000 for Sherwood, Bush only obliquely addressed the controversy.

He praised Sherwood as "the right man to represent" his district, because of policy positions ranging from taxes to Iraq to highway money. Bush then offered effusive admiration for Sherwood's wife, Carol, who sat beaming beside her husband on the dais behind the president after mostly staying out of view during the campaign.

Bush called her a "caring and courageous woman" because of a letter she wrote to constituents over the weekend, in which she denounced Sherwood's opponent, Democrat Chris Carney, for airing campaign ads about the affair.

The president's main message at the event was that the Iraq war is part of the broader anti-terrorism effort.

He warned ominously that Democratic control of Congress would result in a chairman of the House tax-writing committee who would cut off funding for troops in Iraq and a House speaker, referring to now-Minority Leader Nancy Pelosi, who voted against a string of bills: renewing the Patriot Act, creating a Homeland Security Department, waging the Iraq war and authorizing a warrantless wiretapping program.

"Given the record of Democrats on our nation's security, I understand why they want to change the subject," Bush said.

Responded Pelosi spokeswoman Jennifer Crider: "Clearly, the president is getting desperate to keep his rubber-stamp Republican Congress if all he can do is try to scare the American people with false claims."

Later, scooping about $500,000 into Allen's campaign account, Bush switched his emphasis to the other pillar of his campaign-trail speeches: that Democrats would preside over an economically damaging increase in taxes on American families and businesses.

The president took the unusual tack of using a Democrat from yesteryear to ridicule the Democrats of today, pointing to President Kennedy's proposal upon taking office to cut taxes across the board, including on capital gains.

"John F. Kennedy was right in 1963 and George Allen and I are right in 2006," Bush said.

The troubles of Sherwood and Allen have made them two of the GOP's more-endangered candidates as the parties head into midterm elections less than three weeks away.

Allen, once considered a potential candidate for the Republican presidential nomination in 2008, is in a now-tightened race with Democratic challenger Jim Webb. Allen has spent weeks battling the fallout from a series of missteps that started when he used what is sometimes regarded as a racial slur against at Webb campaign staffer of Indian descent. Bush made no mention of Allen's troubles.

Webb, gaining ground in polls and on the incumbent's financial advantage, is drawing help from national Democrats. On Thursday, former President Clinton was also in Virginia, raising money for Webb at the home of former Sen. Charles Robb.

Last week, White House press secretary Snow was in the position of defending Sherwood as a sinner who, like everyone else, is in need of forgiveness and Allen as "not a bigot."

On Thursday, Snow said the president had not changed his mind on either of those points — though he declined to repeat them — and insisted there was no downside to campaigning for the two troubled Republicans.

Anti-war protests awaited Bush at both fundraisers, with the larger and more boisterous crowd in Richmond yelling "Impeach Bush" as his limousine pulled up.