Establishment Republican lawmakers worry that their party might pursue a neoisolationist foreign policy if the populist Tea Party movement continues to have an influence in American conservative politics.

National security hawks have also voiced dissatisfaction with the current top tier of Republican presidential candidates, all of whom advocate a speedy withdrawal from Afghanistan.

Former governors Mitt Romney and Jon Huntsman, both of whom are perceived as moderate, pro-business candidates, agree that America’s heavy military presence in Afghanistan doesn’t serve its national interest anymore. Romney, who previously tried to secure the Republican nomination in 2008, believes that American troops “shouldn’t go off and try and fight a war of independence for another nation.” He and Huntsman were also skeptical of the Western intervention in Libya.

Former House speaker Newt Gingrich, who continually raises the specter of militant Islamism, opposed arming the anti-government forces in Libya, warning, during a primary debate in New Hampshire this summer, “We have no idea what percent of the Libyan rebels are in fact Al Qaeda.”

Rick Perry, perhaps the most hawkish among Republican doves, is compared to former president George W. Bush but vows to refrain from the sort of “military adventurism” that characterized the neoconservative policy in the Middle East. During a televised debate with his fellow contenders in Tampa, Florida on Monday, he added that’s “it’s time to bring our young men and women home as soon, and obviously as safely, as we can” from Afghanistan.

“I’m disappointed that some people in our party are not embracing the concept that the outcome in Afghanistan will determine our national-security fate for decades to come,” Lindsey Graham of South Carolina told Foreign Policy after the debate. An influential member of the Senate Armed Services Committee, Graham was critical of the president’s plans for withdrawing from Afghanistan when he unveiled them this summer, fearing that it would “undercut a strategy that was working” and lead other NATO countries to retreat “at a faster pace now.”

Along with Arizona senator John McCain, the Republican Party’s presidential candidate against Barack Obama three years ago, Graham also said to be “deeply troubled” by the planned drawdown in Iraq where as few as 3,000 American soldiers could remain to train Iraqi security forces next year.

Graham and McCain both called for a bigger American role in the NATO mission in Libya where the alliance enforced a no-fly zone to protect civilians from repression after the regime there had deployed force against peaceful protesters in February. Few Republicans supported them in that effort.

McCain hasn’t singled out any of his party’s presidential hopefuls for criticism but does warn against the growing isolationism in the Republican ranks which he attributes to tough economic times. Both President Obama and former Utah governor Huntsman favor “nation building at home” rather than spending billions of dollars trying to erect a stable government in Kabul. McCain told ABC News in June that the United States “abandoned Afghanistan once and paid a very heavy price for it in the attacks of 9/11.”

Part of the Republicans’ newfound isolationism also stems from their role as an opposition party. Obama promised to end America’s involvement in Iraq altogether during his first term in office and while he is close to making good on that pledge, he escalated the conflict in Afghanistan with some 30,000 surge troops who will only start coming home during election year. Meanwhile, both wars are deeply unpopular

According to an ABC News/Washington Post opinion poll conducted over the summer, more than half of Americans believe that the war in Afghanistan has not been worth fighting. 73 percent of respondents said that the United States should withdraw a substantial number of troops from the country this year although the announced deadline for retreat is 2014.

Robert Gates, who resigned as defense secretary two months ago, in June urged skeptics of the war to wonder, “what’s the cost of failure? We’ve invested a huge amount of money here,” he said, along with many hundreds of lives lost. He later told CNN that “failure is a huge challenge for the United States” and could have “costs of its own that will linger with us for a longer time as was the case in Vietnam.”

The parallel with the Vietnam War is appropriate, he told Newsweek. “That is we came to the right strategy and the right resources very late in the game. President Obama, I think, got the right strategy and the right resources for Afghanistan — but eight years in.”

Besides a narrower, more nationalist foreign policy, the Tea Party champions fiscal austerity above all else and has helped shape the debate about deficit spending in Washington DC. Democrats and Republicans now agree on the need to cut expenditures although the former also want to raise taxes whereas the latter are wary of defense cuts.

If operations in Afghanistan and Iraq were to come to an end, total defense outlays would be reduced by roughly one fifth. The Pentagon would still be spending hundreds of billions of dollars on pay and benefits and housing for personnel as well as operations, maintenance and procurement.

Robert Gates identified some $400 billion worth of cuts in defense spending over the next ten years before he left office. He cautioned against “steep and unwise reductions in defense” if they were enacted because of “tough economic times or the winding down of a military campaign” but deeper cuts could be ahead unless a bipartisan congressional committee agrees to at least $1.2 trillion in federal spending reductions by November.

As part of August’s agreement to raise the nation’s legal debt limit, members of both major parties must find common ground or $600 billion in defense spending is automatically cut.

The very national-security hawks who have criticized the Tea Party’s isolationist streak are already lined up for a fight over the military budget. “Defense spending is not what is sinking this country into fiscal crisis,” Senator McCain said last month, “and if the Congress and the president act on that flawed assumption, they will create a situation that is truly unaffordable — the hollowing out of American military power and the loss of faith of our military members.”

The Senate Defense Appropriations Subcommittee did agree to freeze defense spending at $630 billion for the next fiscal year which is $26 billion less than was requested by President Obama and nearly $20 billion less than was approved by the conservative majority in the House of Representatives.