June 11 (Bloomberg) -- John McCain might like to give Joseph Lieberman another shot at the vice presidency, this time as a Republican.

The two senators have grown close in this election year. They are joined at the hip on foreign policy, staking their political futures on support for the war in Iraq. They also share a reputation as mavericks, which, in Lieberman's case, forced him to quit the Democratic Party in 2006, after losing Connecticut's senatorial primary and running as an independent.

For his part, McCain, 71, has built his campaign around his appeal to independent voters. ``You can't win with Republican votes alone,'' said Mark Salter, a senior campaign adviser, who declined to handicap the likelihood of Lieberman on the ticket.

While picking Lieberman as his running mate would allow McCain to reaffirm his identity as a trans-partisan politician, it also would burn the social conservatives who have propelled every Republican victory since 1980 and who may bolt the party.

``If he picks a pro-choice candidate, it will suppress the base,'' said Richard Land, a leader of the 16-million-member Southern Baptist Convention, based in Nashville. McCain ``can't win without evangelical support.''

Senate Record

Evangelicals need look no further than Lieberman's Senate record -- which includes support for abortion rights, gun control, gay civil unions and stem-cell research -- to find reasons to reject him.

Lieberman, who was Democratic Vice President Al Gore's running mate in 2000, would be a ``calculated risk'' for McCain, said Dave Carney, a Republican strategist.

Many in McCain's party are skeptical the Arizona senator would forsake core party voters.

``I think Lieberman is an unlikely choice,'' said Whit Ayres, a Republican pollster. ``He is at such variance with a great many Republicans.''

Evangelicals, who have balked at accepting McCain, have pressed him to choose a running mate with what they consider impeccable credentials on social issues. For the most part, he has equivocated, leaving the door open to a Lieberman surprise.

Anti-Abortion

At a May 29 town hall meeting in Milwaukee, McCain was asked by a self-described evangelical activist if conservatives would be able to support his vice presidential choice. McCain responded ``I certainly hope so,'' and cited his record of opposing abortion.

``But I also think that we need to be a very large party, and I think we can have disagreements on specific issues,'' said McCain, who was courted by the 2004 Democratic presidential nominee, Massachusetts Senator John Kerry, to join him on a unity ticket.

Lieberman, 66, is showing a penchant for accommodation. He has gone further than McCain in signaling a willingness to embrace evangelical leaders. A devout Jew, Lieberman is scheduled to speak next month at a pro-Israel conference sponsored by the Reverend John Hagee. McCain rejected Hagee's endorsement in late May, after the disclosure that the Texas televangelist said the rise of Adolf Hitler was part of God's plan to help the Jews resettle in Palestine.

On the stump for McCain, Lieberman never mentions his positions on social issues or his mainstream Democratic views on the economy and the role of government. Instead, he sticks to praising his fellow senator's tough line on Iraq, foreign policy and terrorism.

Defense Secretary

These overtures, while appreciated, aren't sufficient, Land said. ``Lieberman would make a great secretary of defense, just not a vice president,'' he said.

For now, campaign aides said McCain treats his friend as a ``sounding board,'' and listens to him on national-security matters more than almost any other adviser.

``They see eye-to-eye on foreign policy,'' said Charlie Black, a senior campaign adviser. ``They don't talk about domestic policy much.'' Black declined to discuss who was being considered as a vice presidential contender.

The two senators have had plenty of time to bond. They travel together to an annual security conference in Munich, and have made many joint visits to Iraq and Israel.

New Hampshire

They also met up this winter in New Hampshire, where Lieberman endorsed the Republican candidate before McCain's victory in the state's January primary.

Since then, Lieberman has been present for high-level political and social gatherings at McCain's retreat in Sedona, Arizona. In March, he attended a meeting where McCain thanked a core group of supporters that included potential vice presidential nominees such as Governors Jon Huntsman of Utah and Tim Pawlenty of Minnesota. He also was a guest last month, when McCain met with another group of prominent Republican officeholders, including Florida Governor Charlie Crist, Louisiana Governor Bobby Jindal and former Massachusetts Governor and primary rival Mitt Romney.

The McCain campaign has tried to use Lieberman as an emissary to Democrats who supported New York Senator Hillary Clinton in the primaries. Lieberman has pushed the notion that Clinton loyalists will defect from the party.

The phones at McCain's campaign headquarters ``have been ringing with disaffected Democrats,'' Lieberman wrote in an e- mail earlier this month on behalf of a new group, Citizens for McCain. ``Many of these supporters are former supporters of Senator Clinton.''

``Friends, that's really what they are,'' said Salter. Lieberman understands ``the appeal of McCain the independent,'' he said. ``He encourages that side of John.''

To contact the reporter on this story: Hans Nichols in Washington at hnichols2@bloomberg.net

Last Updated: June 11, 2008 00:01 EDT