Updated: 10:51 p.m.

Rep. John Tanner (D-Tenn.), a leader of the Blue Dog Coalition, announced Tuesday night that he has decided to step down next year at the end of his 11th term. The news had Republican operatives giddy over what they believe to be evidence that Democrats are facing a tough midterm election cycle.

But Tanner said in a statement that he had considered retiring in 2007 but stayed on after he earned the chance to serve as president of the NATO Parliamentary Assembly.

“We believed we owed it to our country to stay and fulfill this term of office as NATO PA President. This mandate expires in November 2010, and therefore, we have made the decision not to seek re-election to Congress,” Tanner said.

Tanner added that he believed his more than two decades in Congress is “an appropriate amount of time to serve, with the voters’ consent.”

“Our nation faces many severe and unrelenting problems,” he added. “I will stay active on these matters and continue my efforts with the Blue Dogs and others of good will to help our citizens come together for the future of our children and grandchildren.”

News of Tanner’s retirement comes just days after Rep. Dennis Moore (D-Kan.) became the first House Member to announce his out-and-out retirement this cycle. Both Tanner and Moore represent conservative districts that are in grave danger of flipping to the GOP with their departures.

Tanner has had little trouble holding his Western Tennessee despite the fact that it went for Sen. John McCain (R-Ariz.) by 13 points in last year’s presidential race. Republicans recruited little-known gospel singer and farmer Stephen Fincher to try to flip the 8th district in 2010, and Fincher has gained recognition for raising some $300,000 for his campaign through the end of September.

“With $1.4 million in the bank, John Tanner opted for retirement rather than be forced to defend the abysmal economic policies of the Obama-Pelosi agenda,— National Republican Congressional Committee spokesman Ken Spain said in a statement Tuesday night. “When a longtime incumbent such as Tanner — who hasn’t faced a credible challenge in over decade — chooses to retire, it speaks to the deteriorating political environment that Democrats have left in their wake after eleven short months.—

Eighteen other House Members — 12 Republicans and six Democrats — are running for other political offices in 2010.