If Mr. Stevens loses his seat, the trial’s implications could be felt on a broad political scale, helping Democrats in their drive to win enough seats in the Senate to give them a filibuster-proof majority of at least 60 votes. Within an hour of the verdict’s becoming public, Democrats in Senate races around the country immediately sought to make the conviction an issue for their opponents, demanding that those who had received money from Mr. Stevens, who was generous with contributions to his colleagues, return it.

If Mr. Stevens wins and insists on keeping his seat, his fate will be in the hands of his Senate colleagues. A senator can be expelled only by a two-thirds vote of the entire Senate, so a conviction does not automatically cost a lawmaker his seat. Since 1789, only 15 senators have been expelled, most for supporting the Confederacy during the Civil War, the Senate Web site states.

In 1982, the Senate Ethics Committee recommended that Senator Harrison A. Williams, Democrat of New Jersey, be expelled because of his conviction on bribery, conspiracy and conflict of interest charges in the Abscam scandal, and in 1995 the committee recommended the expulsion of Senator Robert W. Packwood, Republican of Oregon, for sexual misconduct. Both men resigned before the full Senate could vote.

Should Mr. Stevens be expelled or resign on his own, the Alaska governor, Sarah Palin, would most likely have to call a special election to fill the vacancy, according to state legal officials.

Image Senator Ted Stevens left court in Washington after the guilty verdict. Credit... Hyungwon Kang/Reuters

Ms. Palin, the Republican nominee for vice president, issued a statement late Monday, saying she was “confident that Senator Stevens will do what’s right for the people of Alaska.”

Governor Palin did not specify what that was. She did ask that the verdict be respected, saying that it “shines a light on the corrupting influence of the big oil service company that was allowed to control too much of our state. It was part of the culture of corruption I was elected to fight. And that fight must always move forward regardless of party or seniority or even past service.”