Oct. 28 (Bloomberg) -- Presidential nominees John McCain and Barack Obama called on Alaska's Ted Stevens to resign from the U.S. Senate a day after his conviction on charges of failing to report more than $250,000 in gifts.

``It is clear that Senator Stevens has broken his trust with the people,'' McCain, a Republican, said in a statement. His running mate, Alaska Governor Sarah Palin, said Stevens should step aside even if he's re-elected on Nov. 4. Democrat Obama said it is ``time to put an end to the corruption and influence- peddling'' in Washington.

Stevens, a Republican, said he is still running for a new term, though political analysts in Washington and Alaska said his conviction makes it more likely he will lose to Democratic challenger Mark Begich. That would boost Democrats' prospects of gaining an ironclad grip on the Senate.

The Democrats, who now control the Senate 51-49, have a chance to expand their majority to 60-40. Achieving that level would strengthen Democratic control over the chamber because the minority often tries to kill legislation by talking it to death. It takes 60 votes to thwart that tactic.

``This could be the sixtieth seat,'' said Larry Sabato, a political scientist at the University of Virginia in Charlottesville who follows congressional political trends.

Democratic Senate candidates in other states, following a strategy suggested by national party officials, immediately sought to use the verdict to put their Republican opponents on the defensive, according to Jennifer Duffy, a senior editor at Washington's nonpartisan Cook Political Report.

`Mentor Convicted'

One Democrat who did so was Bruce Lunsford, who is running against Senate Republican Leader Mitch McConnell of Kentucky. The Lunsford campaign headlined its release, ``Mitch McConnell's Mentor Convicted.''

Stevens's fellow Republicans weren't urging him to stay in the Senate race. National Republican Senatorial Committee Chairman John Ensign of Nevada said in a statement yesterday that he was disappointed to see Stevens's ``career end in disgrace.''

McConnell said in a statement that Stevens ``was found guilty by a jury of his peers, and now must face the consequences of those actions. As a result of his conviction, Senator Stevens will be held accountable so the public trust can be restored.''

Stevens isn't required by law to give up his Senate seat. He can only be removed by a full Senate vote on a recommendation by its ethics committee. Such a process would likely take until next year and would move forward only if he is re-elected.

Dignity of Senate

``Senator Stevens must now respect the outcome of the judicial process and the dignity of the United States Senate,'' Senate Majority Leader Harry Reid, a Nevada Democrat, said in a statement.

Alaska Republican Don Young, a congressman also facing a difficult re-election bid, backed Stevens.

``Senator Stevens has done more for our state than anyone in Alaska's history, and I ask Alaskans to rally behind him with their support,'' Young said.

Stevens, 84, was convicted by a federal jury in Washington of all seven counts of failing to report more than $250,000 in home improvements and other gifts from Veco Corp., an Alaska oil- services company, and its founder, Bill Allen. He is free without bail pending a sentencing date to be scheduled later.

In a statement after the verdict, Stevens proclaimed his innocence, vowed to remain in the race and accused federal prosecutors of ``unconscionable'' behavior.

Will Fight Verdict

``I will fight this unjust verdict with every ounce of energy I have,'' Stevens said. ``I ask that Alaskans and my Senate colleagues stand with me as I pursue my rights. I remain a candidate for the United States Senate. I will come home on Wednesday and ask for your vote.''

Sabato's latest estimate has the Democrats ending up with between 57 and 61 Senate seats, with Alaska among the ones in play. Duffy says her calculations indicate the Democrats need the Alaska seat to reach 60.

The Democrats need to score a net gain of nine seats to reach 60. According to the latest average of polls listed on the political Web site realclearpolitics.com, Democratic candidates are ahead in Senate races in eight states currently represented by Republicans and trail by small margins in two others.

Duffy said the Democratic Senatorial Campaign Committee sent a memo to party candidates in competitive races last week urging them to link their Republican opponents to Stevens as much as possible in the wake of a conviction.

Democratic Contenders

Several Democratic contenders quickly did so yesterday, including Ronnie Musgrove of Mississippi, Jeff Merkley of Oregon, Kay Hagan of North Carolina and Lunsford, Duffy said.

A spokesman for the Democratic Senatorial Campaign Committee, Matt Miller, declined to comment. ``I'm not going to talk about electoral politics at this point in time,'' DSCC Chairman Senator Charles Schumer told Bloomberg Television when asked about the Stevens verdict.

Two polls taken before the verdict showed Stevens, the longest-serving Republican in the Senate, in a statistical dead heat with Begich, 46, the mayor of Anchorage.

An Ivan Moore Research survey of 500 likely voters taken Oct. 17-19 found Begich with 46 percent and Stevens with 45 percent. A Rasmussen Reports poll taken Oct. 6 had Stevens at 49 percent and Begich at 48 percent. Both leads were well within the margin of error.

Polls an Improvement

Those findings represented an improvement for Stevens. Begich led by 17 percentage points in a Moore poll in the immediate aftermath of the indictment on July 29 and by 4 points in a Moore survey taken Oct. 3-6.

The conviction will likely tip the race against Stevens, said Democratic pollster Moore and Marc Hellenthal, an Anchorage- based pollster-consultant who often works for Republicans. ``The comprehensiveness of the verdict certainly makes it apparent to me that Ted Stevens will not win,'' Moore said.

Duffy, who specializes in analyzing Senate races, said the verdict was ``obviously the worst possible outcome, not only legally but politically,'' for Stevens.

Still, ``Let's see what he says and see how voters react to it,'' she said. ``I don't think Alaska voters are all that predictable.''

Dave Dittman, an Anchorage-based Republican consultant and pollster, said Stevens used the trial to tell his side of the story to Alaskans and try to taint the case by exposing prosecutors' failure to disclose some evidence favorable to him.

`Chance to Rebut'

``The trial has been very helpful to him because it has given him the chance to rebut these claims,'' Dittman said in an interview last week.

Sabato disagreed, saying the evidence that Stevens got gifts including home renovations, a gas grill and a power generator damaged his reputation with voters in Alaska.

``Alaskans have found out some unpleasant things about Uncle Ted,'' Sabato said, referring to Stevens' home-state nickname. ``There's no way he looks good. They've read details about the gifts. It's not a positive for an 84-year-old man seeking another six years.''

Sabato said he found irony in the fact that a jury in the District of Columbia -- where residents aren't represented in the Senate and have only a non-voting delegate in the House --could play such an outsized role.

``It's interesting that a jury in D.C. could be deciding who fills the Alaska Senate seat and whether the Democrats get to sixty,'' he said. ``These people with no real vote could be deciding who controls Congress.''

To contact the reporter on this story: Ken Fireman in Washington at kfireman1@bloomberg.net

Last Updated: October 28, 2008 16:57 EDT