Gore planned to offer Lieberman the job by phone on Monday, according to several Democrats familiar with the vice president's thinking, all speaking on condition of anonymity. Lieberman has indicated he will accept.
Picking the moderate Democrat and self-styled moral crusader signals an effort by Gore to win over independent and Republican voters and distance himself from President Clinton's controversies. Lieberman was the first Democratic lawmaker to openly criticize the president's conduct with Monica Lewinsky. Polls show Republican George W. Bush benefiting from the so-called "Clinton fatigue.''
The sources said Gore made his decision after discussions late Sunday night and early Monday morning with top advisers, including former Secretary of State Warren Christopher, who headed up his search process; Gore's brother-in-law Frank Hunger; his wife, Tipper; and campaign chairman Bill Daley.
The vice president and his running mate will appear together at a noontime rally Tuesday in Nashville, the sources said.
Lieberman, 58, beat out five other finalists: Sens. Evan Bayh of Indiana, John Edwards of North Carolina and John Kerry of Massachusetts; House Minority Leader Dick Gephardt of Missouri; and New Hampshire Gov. Jeanne Shaheen.
The Gore campaign hoped Lieberman's selection would be a bold stroke heading into next week's Democratic National Convention in Los Angeles. He trails Bush in polls after last week's GOP convention.
One Democratic ally said Gore was driven in part by a need to make a pre-convention splash, which Lieberman's religion provides. The source said the vice president has been disturbed by polls giving Bush a double-digit edge and fears the election will slip away unless he uses this critical two-week period to gain significant ground, particularly among independents and women.
A Democratic centrist, Lieberman would amplify Gore's support of fiscal discipline and middle-class tax cuts, the sources said. Gore considers his pick a respected voice of independence and integrity, and the sources drew a contrast to the GOP ticket's ties to special interests.
Gore will also contrast the tickets as New Guard vs. Old Guard politics, the sources said.
Gore's selection of an Orthodox Jew is a first.
Because he and his wife, Hadassah, observe the Jewish Sabbath from sundown Friday to sundown Saturday, Lieberman is ostensibly prohibited from working.
The senator has interpreted this to mean he may still work during that time but only to promote "the respect and protection of human life and well-being.'' He has said he will vote on legislation and participate in important meetings on the Sabbath but won't campaign then. He skipped one of his state nominating conventions because it was held on the Sabbath.
While critics brand Lieberman a liberal who votes for abortion rights, gun control and tax hikes, Democrats say he's more conservative when it comes to issues such as defense spending and family values.
"This election is a battle for who wins the American middle,'' Senate Minority Leader Thomas Daschle said before Gore made his choice. "With the Gore-Lieberman ticket, you see a real opportunity for Democrats to pick it up.''
As rumors of a Lieberman pick swirled during the past few months, the senator kept the vow of silence he pledged to Gore, a friend he has called the "most responsible vice president in our history.''
Not since John F. Kennedy was elected as the nation's first Catholic president has religion been much of an issue in a White House race. The sources close to Gore noted that Kennedy was nominated 40 years ago in Los Angeles.
Lieberman may have galvanized his role as the conscience of Congress two years ago when he was one of the first senators to criticize Clinton for his tryst with former White House intern Monica Lewinsky.
"Having criticized Clinton gets him points from the other side,'' said Howard Reiter, a political science professor at the University of Connecticut.
His colleagues agree.
"A lot of problems Gore is having in attracting white men and suburban women come from the connection to the Lewinsky situation,'' said Sen. John Breaux of Louisiana.
But his condemnation of Clinton's behavior may have been more of a personal move than a political one; he was criticizing a friend. Lieberman and Clinton are Yale Law School graduates, and Clinton worked on Lieberman's state Senate campaign. In 1992, Lieberman returned the favor by being the first politician in the Northeast to endorse the Arkansas native's presidential bid.
In 1998, Lieberman and conservative former Education Secretary William Bennett began handing out "Silver Sewer Awards'' to single out and shame producers of sexually explicit and violent films, music, television programs and video games. However, in his most recent financial disclosure forms, Lieberman listed holdings of Fox and CBS stocks â€“ two companies awarded "Silver Sewer'' status.
Although he carved a niche for himself as a liberal reformer during his 10 years as a state senator, Lieberman's move to the middle gives him appeal among Republican voters and politicians, some say.
In Connecticut, Lieberman has gained admiration from Republican Gov. John G. Rowland, who recently called the senator "a great friend of mine'' while endorsing Lieberman's Senate rival.
While Lieberman is allowed to continue his Senate race while campaigning with Gore, a promotion to vice president would require resignation from the Senate â€“ assuming he is re-elected â€“ and mean Rowland would be able to appoint Lieberman's successor to serve until the next state election in 2002.
As state attorney general in the 1970s, Lieberman focused on consumer rights issues. His Senate record on the environment, education, defense, foreign affairs and economic development are cited by his advocates in Gore's inner circle.
The sources said Lieberman satisfies Gore's criteria for vice president: He can assume the presidency at a moment's notice; Gore trusts him; and he shares Gore's commitment to fight for American families.