By Greg Giroux, CQ Staff

Two-term Louisiana Democratic Sen. Mary L. Landrieu has drawn a challenge for her 2008 race from a statewide elected official: Republican John Kennedy, the state treasurer and — until quite recently — a Democrat. Kennedy’s entry, which he announced Thursday on his campaign Web site, reinforces Landrieu’s status as one of a very few Democratic senators up for election next year who have to worry about their re-election prospects.

In fact, the Louisiana contest, rated Leans Democratic by CQ Politics, is the only one ranked as highly competitive among the 12 races for Democratic-held seats that are up in 2008. By contrast, the contest for one Republican-held seat, in Virginia, is currently rated by CQ Politics as a likely Democratic takeover; the races for four other GOP seats, in Colorado, Minnesota, New Hampshire and New Mexico, are rated No Clear Favorite; and two others, in Maine and Oregon, are in the competitive Leans Republican column.

This is a key reason why a recent overview on the 2008 elections, published on CQ Politics and in the CQ Weekly magazine, found that the Democrats at this point in the election cycle appear more likely to make gains in the Senate than to lose enough seats to cost them their current narrow majority.

With their opportunities few and far between, Republican strategists put a high premium on encouraging Kennedy to challenge Landrieu in Louisiana. A Kennedy Senate bid had been rumored for months, and talk of a likely campaign intensified after the longtime conservative Democrat switched to the Republican Party in August. His official decision came on the heels of a trip to Washington, D.C., to meet with Republican leaders, and after a string of Republican electoral victories in Louisiana that included Republican Rep. Bobby Jindal ’s election as governor on Oct. 20 (when Kennedy was re-elected without opposition as treasurer) and Republican gains in state legislative elections that concluded Nov. 17.

“I want you to be the first to know that today I will take the first steps and file the necessary paperwork to run for the United States Senate in 2008,” Kennedy said in his Web-posted message. “I plan to officially kick off the campaign early next year.”

He added, “Over the next few months, I will lay the groundwork of support for an aggressive campaign that will focus on a frank discussion of the issues and how I will help move Louisiana forward working in tandem with our new reform leadership in Baton Rouge,” a reference to Jindal’s election to succeed retiring Democratic Gov. Kathleen Babineaux Blanco .

Kennedy is no stranger to U.S. Senate politics. He ran for the state’s other seat in 2004, finishing third in an all-candidate, single-ballot election. The field was topped by Republican David Vitter , then a House incumbent, who won outright by taking a majority (51 percent) of the vote; Democratic Rep. Chris John took 29 percent, well behind Vitter but well ahead of Kennedy’s 15 percent.

Louisiana has since adopted a system of separate party primaries for congressional elections — typical of those held in the other states — which takes effect in the current election cycle and eliminates the single-ballot “jungle primary” system that has been in effect for decades. Neither Landrieu nor Kennedy is expected to face significant intraparty opposition in their nominating contests next Sept. 6.

Landrieu has been preparing for a competitive re-election contest: She raised $3.2 million in the first nine months of this year, and her campaign had $3.4 million left to spend as October began. As the senior senator of the state that was devastated by hurricanes Katrina and Rita in 2005, Landrieu has focused on securing federal funds for coastal protection, housing and other recovery programs.

The conservative-leaning Southern state is far from a slam dunk for the Democratic incumbent, though. Aside from Jindal’s win for governor and Vitter’s hold on the other Senate seat, five of the state’s seven U.S. House seats are held by Republicans. GOP presidential candidates have carried the state in five of the past seven elections, with the exceptions being the 1992 and 1996 wins by Democrat Bill Clinton of neighboring Arkansas.

Landrieu herself has had to battle to close victories in her two previous Senate races. She was first elected in 1996, narrowly defeating Republican Woody Jenkins to succeed retiring Democratic Sen. J. Bennett Johnston Jr. Landrieu captured a second term in 2002, defeating Republican Suzanne Haik Terrell in a runoff election.