If sources are true, former Massachusetts governor Mitt Romney has selected Wisconsin congressman Paul Ryan as his running mate, with the formal announcement to come Saturday morning.

Ryan is most well-known for his strong views on budget policy — think of him as the United States’s version of George Osborne.

He’s become something of the intellectual spokesman for the Republican Party on budget matters in the post-Bush era — his proposed budget would cut massive amounts of spending out of the federal government, transform Medicare into a voucher program and render other federal programs virtually unrecognizable from their current form.  To the massive anti-government ‘tea party’ view that has emerged in the U.S. center-right since the bailouts of former U.S. president George W. Bush and former Treasury secretary Hank Paulson and the election of U.S. president Barack Obama, Ryan represents somewhat of a true believer in effecting a reduction in government spending.

In other words, Ryan’s not being picked for his foreign policy bona fides, but rather for other concerns — his Midwestern background, his conservative credentials and his wonky credibility (to the American right, at least) on budget matters.

But what would a Vice President Ryan add to foreign policy?  Given that the vice presidential pick is perhaps the most important decision Romney will make before his (potential) election as U.S. president, given that the pick telescopes Romney’s own worldview to some degree, given the influence of recent former vice presidents Dick Cheney and Joe Biden on foreign policy, and given the reality that Ryan would be a heartbeat away from the presidency, it’s a question worth asking.

Uri Friedman, writing for FP Passport, tried to answer the question back in April in a primer on Ryan’s foreign policy — the consensus is that Ryan prescribes a healthy dose of American exceptionalism, but fundamentally remains a more realist, liberal hawk than a neoconservative crusader.

When it comes to slashing U.S. military spending, however, it seems that the Pentagon is the one area Ryan would spare from his federal budget cuts:

Ryan’s 99-page “Path to Prosperity” plan, released last month, provoked an outcry in calling for boosting military spending while slashing the international affairs budget — funding for entities such as the State Department and USAID — by nearly $5 billion. When Ryan said “we don’t think the generals are giving us their true advice” in reference to the military budget, he was quick to walk back his comments. “I really misspoke,” he explained.

Otherwise, when it comes to foreign policy, Friedman notes, in sum, Ryan’s a blank slate:

Ryan’s worldview, in other words, appears to be a bit of a Rorschach test. And in a general election where appealing solely to the Republican base just won’t cut it, that might be exactly what Romney needs.

The Weekly Standard, marking a key Ryan foreign policy speech in June 2011, applauded his stance in favor of American exceptionalism:

“A world without U.S. leadership will be a more chaotic place,” Ryan said. “A place where we have less influence, and a place where our citizens face more dangers and fewer opportunities. Take a moment and imagine a world led by China and Russia.”

Ryan spoke at length about American exceptionalism as it relates to America’s role in the world. “America is an idea,” he said. “And it was the first nation founded as such. The idea is rather simple. Our rights come to us from God and nature. They occur naturally, before government.”

This belief in the American idea, Ryan said, should inform the nation’s foreign policy. “Now, if you believe these rights are universal human rights, then that clearly forms the basis of your views on foreign policy,” he said. “It leads you to reject moral relativism. It causes you to recoil at the idea of persistent moral indifference toward any nation that stifles and denies liberty, no matter how friendly and accommodating its rules are to American interests.”