With the FBI escalating investigations into Reps. John Doolittle (R-Calif.) and Rick Renzi (R-Ariz.), Republicans again find themselves dogged by the corruption issue that helped sink their House majority in 2006 — and now face the prospect of a relatively safe seat being put in play next year.

The strong Republican advantage in Doolittle’s northern California 4th district and the presence of a deep bench of potential replacements there mean the GOP is probably better off if Doolittle does not run for re-election. But Renzi’s northeastern Arizona 1st district is competitive, and Democrats could be in command there absent Renzi and his unique ability to secure the support of the area’s key American Indian voting bloc.

“I think what we’re seeing is a continuing fallout from the culture of corruption of the last Congress,” Democratic Congressional Campaign Committee Chairman Chris Van Hollen (Md.) said Friday, recycling one of the DCCC’s favorite 2006 campaign slogans and signaling that Democrats would once again play the ethics card in an effort to win seats.

Republicans on Capitol Hill and in Arizona and California were scrambling late last week to get a handle on the political fallout from the April 13 FBI raid on Doolittle’s Virginia home and similar action Thursday at an Arizona insurance office with ties to Renzi’s family.

But the Members themselves remained steadfast in their determination to weather the storm.

In a conference call with California reporters on Friday, Doolittle said he fully intends to run for re-election in 2008 and vowed not to resign, according to his spokesman, Brian Jensen.

Doolittle, Jensen said, “remains extremely confident that it will come out that he and his wife haven’t done anything illegal or immoral.”

Renzi’s office did not respond to repeated requests for comment on Friday.

With Doolittle’s ties to now-jailed GOP lobbyist Jack Abramoff and the fact that he was paying his wife to be his fundraiser hanging over him in the previous election, the Congressman barely squeaked out a win against a liberal Democrat in one of the most conservative districts in the country, leading many Republicans to believe the latest ethical dust-up could sink him in 2008.

One California Republican operative familiar with Doolittle’s district predicted that the Congressman would ultimately not run for re-election in 2008.

This operative speculated that Doolittle might even resign before his current term concludes, though not before determining how to pay for his lawyers without his Congressional paycheck. Doolittle has been in elective office for most of his professional career and is not particularly wealthy.

However, one Republican official in Doolittle’s district predicted that the embattled Congressman would survive, just as he did in November, when he beat police administrator Charlie Brown (D) 49 percent to 46 percent.

“He has an amazing reserve of good will in the district,” said Placer County Republican Party Chairman Tom Hudson. “He has a well-earned reputation for personal honesty and ethics. I think he’s kind of the gold standard, that’s why he’s been able to weather this storm.”

In Arizona, Republicans were still grappling with the possibility that Renzi could be forced to resign at some point and were trying to figure out who they have to replace him on the ballot if he doesn’t run for re-election.

The Arizona Republican Party had no comment Friday. But a GOP insider based in the Grand Canyon State acknowledged that without Renzi, the 1st district becomes much more competitive and far from the lock it has been under the wealthy Congressman.

“It’s a seat that could easily go Democratic. At this point we’re exploring all of our options,” this Republican said. “But until things pan out and we see what happens … we’re going to stick with Renzi.”

A second Arizona Republican cautioned that the 1st district is not as competitive as many strategists believe and suggested that Republicans have the perfect candidate waiting in the wings to replace Renzi.

This GOP operative said former state Senate President Ken Bennett — a Mormon from Prescott — would be a strong replacement for Renzi. According to this insider, the considerable community of Mormon Democrats that populates eastern Arizona would be an electoral boon to Bennett and would help him rack up larger victories than Renzi.

“Renzi has made good strides with Indians, and that’s helpful. But you don’t necessarily need the Indian voting bloc to keep that district,” this Republican said.

Republicans on Capitol Hill and in Arizona and California declined to publicly admonish Doolittle and Renzi.

However, they did not defend the two Members either, and many privately acknowledged that the situation could be politically damaging to the House GOP’s effort to convince voters to restore Republicans to power in 2008. In the previous cycle, the Republicans lost a handful of safe seats due to the unethical behavior of their incumbents.

The willingness of GOP leadership and the National Republican Congressional Committee to stand by ethically clouded incumbents appears to be diminished since the party lost its majority. And although the NRCC remained relatively quiet on the Doolittle and Renzi matters, the committee’s leaders vowed to retain control over the two Members’ seats — though not necessarily with the help of the two incumbents in question.

“The responsibility of the NRCC is to rebuild the Republican majority. We will continue to make the decisions and the steps necessary to ensure that we are successful in those efforts,” said NRCC spokeswoman Julie Shutley. “We have every confidence that both of these seats will still be in the red column after Election Day.”

The raid on Doolittle’s home was part of an ongoing investigation into the connections between Doolittle’s wife, Julie, and Abramoff. But it remained unclear at press time Friday why investigators raided Patriot Insurance Agency — listed as an asset of Renzi’s wife, Roberta — although it is no secret that the Arizona Republican has been a target of the Justice Department for some time.

While both Doolittle and Renzi maintain that the investigations ultimately will exonerate them, each temporarily stepped down from key committee posts in the aftermath of the raids, with Doolittle relinquishing his seat on Appropriations and Renzi vacating his slot on Intelligence.

If Doolittle resigns or does not run for re-election, political observers say the Sacramento-area 4th district should be easy for Republicans to retain, considering the GOP’s deep bench of local state legislators and other elected officials. But the raid on the Renzi-affiliated business has caused hopeful Democrats to reshuffle their list of prospective candidates, as Arizona’s 1st district appears more winnable to them in light of Renzi’s deepening legal troubles.

“Having voters fully aware that their Congressman is under investigation and being raided by the FBI is going to help Democrats truly run against him,” Arizona Democratic Party spokeswoman Alice McKeon said.

Among the candidates Democrats in both Arizona and Washington, D.C., are eying to run in the 1st district are state Rep. Anne Kirkpatrick of Flagstaff; attorney Jim Ledbetter of Cottonwood; attorney and 2006 nominee Ellen Simon; and state Department of Environmental Quality Director Steve Owens.

In California’s 4th district, at least a half-dozen Republicans would have to be considered viable candidates in Doolittle’s absence, including state Assemblymen Ted Gaines, Rick Keene and Roger Niello, and state Sen. Dave Cox.

Jennifer Yachnin contributed to this report.