What a difference a year makes. The 2010 Senate landscape has been rocked by North Dakota Democrat Senator Byron Dorgan’s stunning announcement Tuesday that he would not seek reelection come November. Retirement announcements from Connecticut Democrat Senator Chris Dodd and Colorado Democrat Governor Bill Ritter came soon after, the latest indicators of a worrisome electoral outlook for Democrats.

The most consequential of these is Dorgan, who has strong approval ratings and decades of double-digit victories under his belt. Far to the left of his constituents and a master at trading his dark suit for a pair of Wranglers and talking like a conservative back home, the numbers tell the real story of where his philosophical heart resides: His 2008 rating from the left-wing Americans for Democratic Action was 90 percent while his American Conservative Union score was 8 percent.

Dorgan has been getting away with this act for years, so why jump ship now? Putting aside any personal reasons, with Democrats misreading their mandate and overreaching in their control of the House, Senate, and presidency, it became more difficult for Dorgan to disguise his true nature. Dorgan went against the will of his constituents by voting for the Senate health care bill: a recent Rasmussen poll showed 64 percent of North Dakotans oppose the bill. Like former South Dakota Senator Tom Daschle in 2004, Dorgan became exposed for who he is.

Additionally, the same Rasmussen poll showed Dorgan losing by 22 points in a hypothetical matchup with popular Republican Governor John Hoeven. Perhaps Dorgan’s internal polls weren’t much better. The looming threat of a strong challenger --something Dorgan has never faced -- combined with growing voter backlash against the Reid/Pelosi agenda did not portend well for him.

North Dakota has had an all-Democratic congressional delegation since 1987, something of a paradox in this solidly red state: The last time a Democrat won the popular vote was Lyndon Johnson’s 1964 landslide; the governorship has been in Republican hands since 1993; and the GOP not only enjoys broad majorities in the state House and Senate but controls every statewide office save one.

All eyes are on Hoeven, who on Tuesday told the Associated Press he plans to reveal his intentions “within a couple of weeks.”

Meanwhile, the state’s other Senator, Budget Committee Chairman Kent Conrad, may think he can sit back and weather the storm until he’s up for reelection in 2012. But if Hoeven eventually wins Dorgan’s seat, trouble lies ahead for Conrad. Just as the high visibility of health care forced North Dakotans to say to themselves, “Dorgan is to the left of me,” a Republican like Hoeven casting opposite votes will leave Conrad exposed and force him to defend his record, day after day, for nearly two years. Naked to the wind, and no longer able to band together with Dorgan, Conrad will have trouble pretending his positions are “moderate” or “reasonable.”

John Kartch is director of communications for Americans for Tax Reform and a Fox Forum contributor.