WASHINGTON -- Republican presidential candidate John McCain continued hammering Russia on Tuesday for its invasion of U.S.-allied Georgia, telling a cheering audience that he had spoken again with the tiny Caucasus country's president to assure him of America's moral support.

The longtime Arizona senator, who had adopted an increasingly tough line against Moscow well before the crisis in Georgia, told a town meeting in Pennsylvania that he had spoken with Mikhail Saakashvili, president of the former Soviet republic, to assure him that "today we are all Georgians."

McCain said Moscow is using "violence against Georgia to send a signal" to "any country that chooses to associate with the West." Russian leaders, he said, must realize they risk "the benefits they enjoy from being part of the civilized world."

Democratic opponent Barack Obama also took on the crisis in the restive Caucasus region, declaring from his Hawaiian vacation that "it is past time for the Russian government to immediately sign and implement a cease-fire. Russia must halt its violation of Georgian airspace and withdraw its ground forces from Georgia, with international monitors to verify that these obligations are met."

Both candidates have joined in severely scolding the Kremlin for invading Georgia, but their words and tone offered a window into the significant differences in how the candidates would conduct future U.S.-Russian relations.

Of the two, only Obama saw room to criticize both sides in the first serious foreign policy crisis to flare since they began their one-on-one battle for the White House, saying Monday that "there is no possible justification for these attacks," while noting that "Georgia should refrain from using force in South Ossetia and Abkhazia, and a political settlement must be reached that addresses the status of these disputed regions."

South Ossetia and Abkhazia are regions in northern Georgia that have broken away under Russian protection. Both have operated on a virtually autonomous basis since shortly after Georgia achieved independence when the Soviet Union collapsed in 1991. Russia has what it calls "peacekeeping" forces in both regions.

The current crisis flared late last week when Georgian forces apparently sought to reassert control in South Ossetia through military attacks on the regional capital of Tskhinvali. Russia responded with overwhelming force, sending in troops, armor and attack aircraft. Georgian President Mikhail Saakashvili immediately sought a cease-fire but was shunned by the Russians, who said he should step down.

On Tuesday, after expressions of outrage in Washington and European capitals, Russian President Dmitry Medvedev ordered a halt to military action and said on national television that his military had inflicted sufficient punishment on Georgia.

Medvedev, however, said he ordered the military to defend itself and quell any signs of Georgian resistance and their were reporters of continued fighting.

McCain, who has called for Russia to be expelled from the Group of Eight, the world's most powerful industrialized countries known as the G-8, gave no ground in his criticism of the Kremlin leadership and what he views as its increasingly autocratic rule.

McCain loses no opportunity to contrast his background -- that includes 5 1/2 years as a prisoner of war in North Vietnam and more than 20 years in the Senate -- to that of Obama, a first-term senator.

He has been highly critical of Obama's stated willingness to negotiate with world leaders whose policies are seen as threatening to U.S. interests and security.

Perhaps the most controversial of proposals by both McCain and Obama were calls for NATO to consider putting Georgia on a faster track for alliance membership, which gives any signatory the promise of protection by all NATO nations in case of attack. Such a move in the case of Georgia would, in theory, have meant NATO military action against Russia.

"NATO's decision to withhold a Membership Action Plan for Georgia might have been viewed as a green light by Russia for its attacks on Georgia, and I urge the NATO allies to revisit the decision," McCain said.

Obama appeared to agree, saying, "I have consistently called for deepening relations between Georgia and trans-Atlantic institutions, including a Membership Action Plan for NATO, and we must continue to press for that deeper relationship."

While the crisis in the Caucasus played out, light was shined on the dark underside of American politics.

The Atlantic magazine reported that Hillary Rodham Clinton's top campaign strategist had advised her to cast Obama during their battle for the nomination as having questionable "roots to basic American values and culture" and use the theme to counter the image that his background is diverse and multicultural.

Obama is the son of a black man from Kenya and white woman from Kansas. He was born in Hawaii, the 50th U.S. state of Pacific Ocean islands that has a diverse culture, and spent part of his childhood in Indonesia.

"I cannot imagine America electing a president during a time of war who is not at his center fundamentally American in his thinking and in his values," top adviser Mark Penn wrote in a March 2007 memo to Clinton, who did not act on the advice.

Meanwhile, a leading Republican moderate with a foreign policy background crossed party lines to endorse Obama, as the Democratic candidate sought to show his appeal to members of both major political parties.

Former Rep. Jim Leach of Iowa was among a group of Republicans who said they are supporting Obama. Obama's campaign said he was also being backed by the Republican mayor of Fairbanks, Alaska, Jim Whitaker.

"I'm convinced that the national interest demands a new approach to our interaction with the world," Leach, a foreign service officer before being elected to Congress, said in a conference call with reporters.

Wendy Riemann, a spokeswoman for Republican candidate John McCain, responded that McCain is the one with a record of reaching beyond party lines.

"A single endorsement does not hide the fact that Sen. Obama has no record of achievement beyond the confines of his party," Riemann said in a statement. "While John McCain has spent his career putting the country first -- ahead of personal and party interests -- Sen. Obama's record is a lesson in partisanship."