A Rasmussen Louisiana poll taken late last week gave incumbent Democratic Sen. Mary Landrieu a comfortable 55-39 lead over Democratic turncoat and Karl Rove recruit John Kennedy, the state treasurer. Another new poll by Southern Media & Opinion Research gave Landrieu a similar 50-38 lead.

On its surface, these polls might appear boring, suggesting yet another predictable third-tier race, like the many that dot the political map every year. In reality, these results portend something much bigger — this seeming blowout in the making is the GOP’s best and pretty much only chance for picking off a Democratic seat in the Senate this year.

And once you get past Louisiana, it only goes downhill for Republicans.

For example, they were once hopeful about challenging freshman Democratic Sen. Mark Pryor in Arkansas. The state gave President George W. Bush a nine-point victory in 2004, and Pryor was the sole Democratic Senate pickup in 2002, aided by a scandal-plagued Republican incumbent. No elected official is more vulnerable than in his or her first reelection battle. Yet Republicans didn’t just fail to field a top-tier candidate to challenge Pryor, they failed to field anyone.

There’s South Dakota, the heavily Republican state where the GOP knocked off former Democratic Senate leader Tom Daschle in 2004. Yet rather than field a top-tier challenger to Democratic incumbent Sen. Tim Johnson, Republicans failed to offer up anything more than third-rate cannon fodder. As Republicans scraped the bottom of the barrel, they ginned up Steve Kirby, former lieutenant governor and venture capitalist who had invested money in a firm that skinned cadavers to manufacture plastic-surgery products (including penis enlargement creams). But Kirby dropped his nascent bid after light was shone on his business practices, and Republicans had no one else.

New Jersey is interesting — a solidly Democratic state that hates its politicians. Republicans, year after year, seduced by the numbers, field their latest “dream candidate,” forgetting that if there’s one thing Garden Staters hate more than their incumbent Democratic politicians, it’s their Republican challengers.

Republicans first chose self-funding Anne Estabrook, but she was forced to drop out for health issues. They then chose self-funding Andy Unanue, a New York club promoter and ousted Goya Foods exec who announced his bid from Vail, Colo. That didn’t go over so well, so they then chose self-funding biotechnology executive John Crowley, who was actually kind of impressive. But he almost got in, dropped out, almost got in again, then dropped out again. All the while Unanue was still in the race, looking like an idiot. He finally quit, leaving Republicans with nothing.

Similarly, “red” Montana and West Virginia will prove easy holds for Democratic incumbents this year.

For their part, Democrats have near-guaranteed pickups in Virginia and New Mexico, are favored to pick up seats in New Hampshire and Colorado, and have toss-up pickup opportunities in Minnesota, Mississippi and Alaska. They are even threatening to make competitive races (at least as much as Louisiana) out of Oregon, Maine and even potentially Texas, Nebraska and Idaho.

Republicans lack any pickup opportunities beyond a possible Sen. Joe Lieberman (I-Conn.) defection. Given the GOP’s tarnished brand, Sen. Barack Obama’s (D-Ill.) ability to run strong in red states, and the 2-1 fundraising gap suffered by Senate Republicans compared with their Democratic counterparts, Democrats will be close to 60 seats by the time the smoke clears this November.

And believe it or not, 2010 is an even more favorable Senate map for the Democrats.

Moulitsas is founder and publisher of Daily Kos .