The combatants in South Dakota’s nip-and-tuck Senate battle have turned their focus to unethical influence peddling, with former Rep. John Thune’s (R) campaign training its fire on the wife of Senate Minority Leader Tom Daschle (D) and Daschle’s camp accusing Thune of exhibiting “moral weakness.”

Heading into the final week of what could be the year’s most critical campaign in terms of shaping the Senate, Thune and his GOP allies launched a pair of attacks questioning the ethics of Linda Daschle’s well-established lobbying practice. In print ads and direct-mail pieces, Republicans accused the Senator of “personally profiting” from his wife’s pharmaceutical industry clients and politically benefiting from her clients’ campaign contributions.

As the National Republican Senatorial Committee touted a poll that showed Thune up 4 points in the race, Daschle’s campaign charged that Thune’s attacks showed “political cowardice, moral weakness and reeks of desperation,” according to Dan Pfeiffer, Daschle’s spokesman.

The Daschle campaign also renewed old charges that Thune violated new campaign finance laws when he served as head of a 527 political committee, which was able to raise unlimited amounts of soft money, for a few months in 2003.

The sharp exchanges demonstrated the heightened anxiety in a race that is going down to the wire, with both sides anticipating a margin of just a few thousand votes — if not much less. The NRSC poll, conducted by McLaughlin & Associates of 400 voters on Thursday and Sunday, found Thune ahead 48.5 percent to 44.5 percent for Daschle, with 7 percent undecided. Democrats dismissed the poll and pointed to a Mason-Dixon poll due out today, anticipating it will show Daschle slightly ahead.

The personal nature and ferocity of the attacks put a renewed emphasis on sticky questions regarding family members of Senators who lobby and the increasingly common practice of Senate candidates running for office while lobbying at the same time.

The Thune campaign took out a full-page ad in Saturday’s Argus Leader, the newspaper of Sioux Falls, that excerpted a report filed with the Senate Office of Public Records showing Linda Daschle’s name on the form for her firm’s lobbying on behalf of Schering-Plough. At the time the company was seeking a patent extension on its anti-allergy drug, Claritin.

Noting that the company paid $470,000 to Daschle’s firm, Baker Donelson Bearman Caldwell & Berkowitz, the Thune ad ends with the line: “Only one candidate has personally profited from big drug companies. That candidate is Tom Daschle.”

The South Dakota Republican Party also sent out a four-page mailer that went after Linda Daschle’s lobbying for airlines that benefited from a post-Sept. 11, 2001, bailout supported by Sen. Daschle and all Congressional leaders as well as by Thune himself.

Thune’s aides stayed on the offensive Monday, suggesting their attacks were based on stories from mainstream or left-leaning publications such as The Washington Monthly, Slate and L.A. Weekly. Dick Wadhams, Thune’s campaign manager, said the “clear conflict of interest Linda Daschle” is involved in was first aired “long before this campaign started.”

“There is literally only one candidate in this race who has personally profited from pharmaceutical companies,” Wadhams reiterated.

Pfeiffer countered that Thune’s old firm, Arent Fox, had the Pharmaceutical Research and Manufacturers of America as one of its biggest clients, contending Thune indirectly benefited from the work of other lobbyists at the firm. The Daschle campaign also circulated old news stories about Thune’s 527, South Dakotans for Responsible Government, which spent $22,000 in soft money in the first three months of 2003.

Amid questions of whether he could use the money to promote his own issues and then eventually run against Daschle, Thune closed the organization, which raised almost all of its funds from a Thune lobbying client.

Questioning Thune’s attempts to “rap himself in South Dakota values,” Pfeiffer said, “In fact, he’s the one who made himself quite wealthy by lobbying for a Washington, D.C. firm.”

An aviation lobbyist since the 1980s, Linda Daschle later served as an administrator for the Federal Aviation Administration in the 1990s. Since joining Baker Donelson after leaving the FAA, Daschle has stipulated on her lobbying forms that she voluntarily does not lobby the Senate.

Senate rules do not require Linda Daschle to do this, and numerous spouses and children of Senators and House Members continue to lobby those bodies as well as their relative-Member. Catherine Stevens, wife of Senate Appropriations Chairman Ted Stevens (R-Alaska), for example, has done Appropriations lobbying in recent years. Another big-time aviation lobbyist is Rebecca Cox, head of government affairs for Continental Airlines and wife of House Homeland Security Chairman Christopher Cox (R-Calif.).

Senate Minority Whip Harry Reid (D-Nev.), whose sons and son-in-law have lobbied his office but are now forbidden from talking to his aides, has proposed new regulations that would establish limits on what family members are allowed to do in lobbying activities. Reid, vice chairman of the Ethics Committee, has not gotten anywhere with his proposal, which he offered to Ethics Chairman George Voinovich (R-Ohio) 10 months ago.

In the past 18 months for which records are available, Linda Daschle’s clients have paid her firm $2.1 million for the services of her and a handful of other lobbyists she works with. Her 2003 tax returns, which Daschle’s campaign gave to local media, show the firm paid her $750,000 last year.

By placing additional restraints on her work, Daschle’s campaign insists that Linda Daschle goes above and beyond what is required by law. They argue that her work stands in sharp contrast to Thune, who continued to lobby this year while campaigning against Daschle. Shortly after losing by 524 votes to Sen. Tim Johnson (D-S.D.) in 2002, Thune set up the Thune Group out of his Sioux Falls home and also opened up shop with Arent Fox in Washington.

In 2003, Senate records show, he brought in $440,000 from his clients. He stopped his work with Arent Fox at the end of 2003, just as he decided to enter the race against Daschle, but kept three clients for the Thune Group.

In the first six months of 2004, while running full time for the Senate, Thune collected $120,000 from those clients — one of which, BPI Technology, gave $20,000 to Thune’s 527 in 2003.

Two freshman Republican Senators are among those who worked for law firms that lobbied government agencies as they were campaigning for office or preparing to mount their campaign. Sen. Norm Coleman (R-Minn.) held a position with a St. Paul, Minn., law firm until July 2002, a few months before Election Day, according to the financial disclosure form he filed in May 2003.

He earned more than $160,000 in little more than a year with the firm.

Sen. Jim Talent (R-Mo.) stopped working with his firm — Arent Fox, the same firm whose D.C. office employed Thune — at the end of 2001, receiving $242,403 for that year.