Convicted Alaska Sen. Ted Stevens conceded defeat Wednesday to Anchorage Mayor Mark Begich (D), officially marking the end of the longest-serving Republican Senator’s 40-year career.

With the majority of outstanding ballots counted by Tuesday evening, Stevens trailed Begich by more than 3,700 votes. He acknowledged the margin was too great for him to overcome with only a handful of votes left to be counted. Because the vote margin was so small, Stevens could have requested a recount.

“I am proud of the campaign we ran and regret that the outcome was not what we had hoped for,” Stevens said in a statement. “I am deeply grateful to Alaskans for allowing me to serve them for 40 years in the U.S. Senate. It has been the greatest honor of my life to work with Alaskans of all political persuasions to make this state that we all love a better place.”

He added that he and his staff are prepared to help Begich with his transition. Begich was not present on Capitol Hill this week for freshman orientation because the election had not yet been called.

Even if Stevens had prevailed, he faced likely expulsion from the Republican Conference as well as the Senate. Under that scenario, Alaska Gov. Sarah Palin (R) would have been able to appoint a successor, presumably a Republican, and a special election would have been required shortly thereafter to fill the vacancy until 2010, when another election would have been held to fill the remaining four years of the Senate term.

Stevens, who was convicted last month on seven counts of corruption, leaves the chamber as the longest continuously serving Republican Senator in history.

The late Sen. Strom Thurmond (R-S.C.) actually served in the Senate longer, but he did not serve consecutive terms and served only 39 years as a Republican.

Stevens, who turned 85 on Tuesday, was first sworn in to the Senate on Christmas Eve 1968. He has held the title of President Pro Tem Emeritus since January 2007. He served as President Pro Tem from 2003 upon Thurmond’s departure until the end of 2006, when Democrats regained control of the chamber.

Sen. Dick Lugar (Ind.) will be the most senior Republican Senator in the 111th Congress. Lugar was sworn in Jan. 3, 1977, the same day as Sen. Orrin Hatch (R-Utah). However, Lugar ranks ahead of Hatch in seniority based on state population.

Sen. Lisa Murkowski (R-Alaska) said in a statement that Stevens’ work in the Senate on behalf of Alaska would continue to be felt for generations.

“Elections are one of the most important things we do as Americans, and I applaud all Alaskans who participated in this historic election,” Murkowski said. “I congratulate Mark Begich on his victory, and I look forward to working with him on behalf of all Alaskans.”