The latest polls show that Republican voters are far from agreeing on a consensus candidate, a presidential nominee who embodies conservative ideals and can win in 2008. Even as that search continues, Arizona's Sen. John McCain has climbed back into contention with a dramatic resurgence showing conclusively that he deserves a second look from the Republican faithful.

In recent weeks, McCain has garnered national-news endorsements from four newspapers; two from traditionally conservative papers, the Manchester, N.H., Union-Leader and the Boston Herald, and two from liberal papers, The Des Moines Register in Iowa and The Boston Globe, that endorsed in both parties' political primaries.

Amidst this impressive, and effectively bipartisan, validation, McCain's candidacy was endorsed by Connecticut Sen. Joe Lieberman, the centrist Democrat-turned-independent. Lieberman's endorsement carries particular political significance. Al Gore's vice presidential running mate in the 2000 presidential campaign, Lieberman has since demonstrated notable political courage and independence by staunchly defending the war in Iraq and the larger, integral struggle against a global terrorist enemy.

Lieberman's endorsement of McCain sends two noteworthy political signals. First, that McCain retains the appeal to independents that distinguished his 2000 primary challenge of George W. Bush and without which Republicans have no chance of winning the presidency in 2008. Second, that McCain's national security credentials are unmatched by any other presidential contender in either political party.

Underscoring that latter point, McCain has also been endorsed by former Secretary of State Henry Kissinger, still the nation's most serious and substantive voice on foreign policy and national security issues. That Kissinger, a notably nonpartisan figure in recent decades, would step out of his customary role of elder statesman to endorse McCain's quest for the Republican presidential nomination qualifies as hugely significant.

What marks McCain as unique are his dual political qualifications - his well-earned reputation for flinty independence combined with his credentials as, in his own words, a "proud Reagan Republican."

McCain dissented from Republican orthodoxy on campaign finance reform, immigration and climate change policy. Yet, over his quarter century of congressional service he's been reliably conservative. The American Conservative Union rates his lifetime voting record in the House and Senate at a staunch 82 percent.

No Republican presidential contender comes close to his record for fiscal responsibility. McCain is a deficit hawk who has warred against pork-barrel overspending and corruption-breeding congressional earmarks by Democrats and Republicans alike. He believes that tax cuts should be matched by spending restraints, a position amply vindicated by experience.

On social issues, McCain is pragmatically conservative without being rigidly doctrinaire. He's firmly pro-life with a voting record to match. He supports the military's "don't ask, don't tell" policy on gays, yet opposed a proposed constitutional amendment banning same-sex marriage on the correctly conservative grounds that this matter should be decided by the states.

He supports free trade, nuclear power as a clean-energy alternative, school choice as an education-reform imperative, lower taxes as a spur to economic growth and the death penalty as a deterrent to crime.

But it's national security that stands as John McCain's strongest qualification for the White House, all the more so in time of war. No one running in either party comes close to McCain's credentials. Unlike every other major presidential contender, McCain has actual military experience; an Annapolis education, years of active duty as a naval aviator, air combat in Vietnam and then five-and-a-half years as a cruelly brutalized prisoner of war in North Vietnam.

He's the ranking Republican on the Senate Armed Services Committee. His grasp of military and defense issues, honed by personal experience and 25 years in Congress, far exceeds that of every other major presidential contender.

His bona fides as a principled maverick willing to speak truth to power are equally impressive. His dissent over the Bush administration's mishandling of the Iraq war led him to call for Defense Secretary Donald Rumsfeld's resignation, and consistently urge more troops and a change in strategy. The manifest success of the current troop surge and its new counterinsurgency doctrine, both strongly supported by McCain, vindicate his Iraq policy.

Beyond troop levels and strategy, McCain's fierce devotion to the cause of American success in Iraq especially distinguishes him. Alone among his presidential rivals, McCain retains a searing sense of America's failure in Vietnam and its tragic costs. He's resolutely committed to preventing Iraq from becoming, in fact, another Vietnam.

In politics as in life, character is destiny. John McCain, the son and grandson of Navy admirals, is steeped in the ethic of service to country. His valor and principles are beyond question, as is his fealty to causes "larger than oneself." Who among his rivals, in either party, can say as much?

A second look at John McCain is the least that Republican voters owe themselves, their party and their country.

Caldwell can be reached via e-mail at robert.caldwell@uniontrib.com.