President Bush goes to Pennsylvania tomorrow to campaign for embattled Republican House members in the Philadelphia suburbs. But one of the candidates isn't expected to be there.

Mr. Bush "is really doing poorly in our state," says Rep. Curt Weldon, explaining why he won't be on hand and hasn't asked for the president's help. "I've got to win this by myself."

Well, almost. Mr. Weldon did invite Arizona Sen. John McCain to his district last month to help him campaign and raise money, and he is thinking about doing it again.

It isn't easy leading your party to victory when a lot of people aren't eager to follow. With Mr. Bush's job-approval ratings skidding as low as 30% in national polls, more Republican candidates face risks in associating closely with him. That is forcing the White House and Republican advisers to improvise a strategy for success.

So far, they are putting Mr. Bush on the road to raise huge amounts of cash -- the $100 million-plus he has raised exceeds the amounts he generated at this point in the past two election cycles -- much of it for state and national committees that can, in turn, contribute to endangered candidates. Republican strategists are also making more use of popular first lady Laura Bush. And they are seeking to boost the president's standing on his most troublesome issues -- notably Iraq, but also immigration and energy -- while highlighting their differences with Democrats and underscoring the importance of local issues.

Still, as Mr. Weldon's case shows, the plan has built-in limitations. While many lawmakers continue to request presidential visits, there are more and more places where an appearance by Mr. Bush could hurt the Republican candidate. While control of Congress remains theirs to lose, for Republicans the situation is certainly complicating matters, particularly as the focus shifts from early-season fund-raisers to late-season barnstorming.

At a Friday fund-raiser for one embattled Republican lawmaker, freshman Rep. Geoff Davis of Kentucky, Mr. Bush even joked about his shrinking political range: Mr. Davis "really wanted Laura" to appear, Mr. Bush said, to laughter from a roomful of northern Kentucky donors. "He said, 'You stay at home, Mr. President. Yes, next time.' Unfortunately, she was tied up."

This week, the awkward distancing is likely to be on display again in Pennsylvania, where Republican incumbents already are under the gun, and some suffered big losses at the legislative level in last week's primary.

Mr. Bush will hold a fund-raiser tomorrow for two at-risk Republican House members in the Philadelphia suburbs, Reps. Mike Fitzpatrick and Jim Gerlach. Both are running in districts where Mr. Bush's 2004 opponent, John Kerry, took 51% of the vote.

But the third Republican in the area, Mr. Weldon, whose district was even friendlier to Mr. Kerry, won't benefit from the event and isn't expected to show up. Instead, Mr. Weldon relied on Mr. McCain to help campaign and raise money.

One local paper in suburban Delaware County quoted Mr. Weldon suggesting that he is running from Mr. Bush, saying, "What am I supposed to do?"

Mr. Weldon explains in a subsequent interview that he is "not really running away from the president." But with Mr. Bush's poll numbers so low, he says, "there's nothing the president can do to help me."

At a recent White House bill-signing ceremony, Mr. Weldon says, the president pulled him aside in an anteroom and said he understood that Mr. Weldon had a difficult race this year. "Just be happy I'm not at the top of the ticket," the president joked, according to Mr. Weldon.

Democrats, of course, are doing their best to turn the 2006 election into a referendum on Mr. Bush. Mr. Weldon's opponent, Joe Sestak, a retired Navy vice admiral, hammers the point that Mr. Weldon is trying to duck his connections to Mr. Bush. "Curt Weldon is worried," Mr. Sestak says. "That's why he's trying to manufacture a separate life, and it won't hold."

Earlier this month, the Democratic National Committee fired off a news release pointing out that a private fund-raiser for Mr. Weldon, headlined by Vice President Dick Cheney, was held in Washington. Until then, the $1,000-a-plate luncheon, held at a lobbying firm, had gone unnoticed in the media. Noting Mr. Bush's low ratings, the DNC said, "maybe that explains why Congressman Weldon held his fund-raiser in Washington, D.C., and not Pennsylvania."

Mr. Weldon says he wasn't dodging, and that the luncheon's location was dictated by his congressional schedule.

Democrats still could overplay their hand, as Republicans did in 1998, when then-President Clinton was on the ropes over testimony concerning his affair with Monica Lewinsky. Republican talk of impeachment backfired at the polls.

For now, it is Republicans who are scrambling as more House seats appear to be at risk. Still, Republican strategists are more confident the party will hold the Senate. They also believe apparent progress in forming an Iraqi government will help, as will movement at home on immigration and tax cuts.

Last week, White House political guru Karl Rove said that internal Republican polls show Mr. Bush remains personally popular despite his low job-approval ratings. That makes it easier for Republican candidates to stand up with Mr. Bush at events -- and rake in the huge amounts of campaign cash he is able to generate.

Ken Mehlman, Republican National Committee chairman, dismisses concerns about Mr. Bush's effectiveness on the campaign trail. While the president's poll numbers are important to candidates, "what I would say is that those ... who've argued that this president is not able to help candidates ought to look at the facts," he says. "He's done more to help candidates than in either '02 or '04."

Write to John D. McKinnon at john.mckinnon@wsj.com

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