WASHINGTON, D.C. -- White House operatives, seeking to give President Bush flexibility in the proposed Department of Homeland Security, are spreading horror stories over Capitol Hill about interference from employee unions. Two examples: Labor leaders are accused of blocking mandatory radiation detectors for Customs agents on the border. Unions are insisting on strict seniority, without regard to language capability, for Customs personnel sent abroad for pre-screening. A footnote: While Senate Democrats are insisting on protecting union rights for the new department, House Republicans say this is one issue where they will not yield. They say they prefer no bill at all. SHORT-TERM FRIST Sen. Bill Frist of Tennessee, mentioned as a possible George W. Bush vice-presidential running mate in 2004, tells friends that in any event he almost certainly will not seek a third Senate term in 2006. Since his upset victory over Democratic Sen. Jim Sasser in 1994, former heart surgeon Frist has been a rising star in the Senate. His colleagues regard him as a future Senate leader if he is not picked for a national ticket in 2004. However, he has made clear he feels two terms and 12 years as a senator is enough. Frist gets high grades as Senate campaign chairman for the 2002 cycle. Unless there is a Republican debacle on Nov. 5, Frist likely will fill the same role for 2004. NEGATIVE IN S.D. Attacks on Democratic Sen. Tim Johnson's lack of support for the Gulf War a decade ago has given Republican Rep. John Thune a boost in the closely watched South Dakota Senate race. Thune has blasted Johnson, then a House member, for suing to keep the elder President Bush from going to war against Iraq in 1991 without first seeking congressional approval, and then voting against the resolution sought by Bush. A TV ad assails Johnson for other anti-defense votes and support from the anti-war Council for a Livable World. Nightly Republican tracking then showed a Thune spurt of 6 to 7 points in the previously even race. A footnote: President George W. Bush, who talked Thune into making the tough Senate campaign, is going all out for him. He has campaigned for Thune twice in South Dakota and will be at Washington's Willard Hotel Sept. 24 for a Thune fund-raiser ($1,000 for the general reception, $5,000 for a private reception). On the next day, all 49 Republican senators will host a $1,000-a-plate Thune luncheon at La Colline restaurant. PRIVATIZED SOCIAL SECURITY? The party leadership's advice to Republican House candidates to avoid Social Security privatization has angered conservative theoreticians who fear a long delay in changing the system. Rep. Tom Davis, the House Republican campaign chairman, has called on the party's candidates to stay away from the issue and especially the word "privatize." Steven Moore, chairman of the supply-side Club for Growth, said in a memo to Davis, "Republicans must run ON the issue of creating Social Security private investment account options, not AWAY from it." A footnote: The latest Republican candidate to avoid the issue is Elizabeth Dole, who forced the withdrawal of a Democratic ad putting her on record for private accounts. Dole enjoys a big lead over former Clinton chief of staff Erskine Bowles for the open Senate seat in North Carolina. MISSISSIPPI'S BARBOUR Former Republican National Chairman Haley Barbour is making clear that he intends to run for governor of Mississippi next year even if State Attorney General Mike Moore, the strongest possible Democrat, makes the race. Word had spread through Washington's lobbyist circles that Barbour would run against embattled Democratic Gov. Ronnie Musgrove but would demur if Moore becomes a candidate. Barbour, a big-time Washington lobbyist who keeps his residence in Yazoo City, Miss., totally denies that report. Trial lawyers, fearing Barbour as an implacable foe, have been prospecting for a better candidate than Musgrove. Former Rep. Wayne Dowdy is mentioned, but they really want Moore -- a well-known figure in Mississippi and nationally for leading anti-tobacco litigation.