The Russian invasion of the Ukraine poses a tremendous challenge to President Obama as his feckless attempts at “resets” of relations with Russia and record of weakness abroad have put him a position where he is forced to respond to a crisis for which he clearly has no appetite but can’t ignore. But he isn’t the only one American politician who should be worrying about Vladimir Putin’s ability to overturn the applecart of Washington politics. Kentucky Senator Rand Paul should be just as concerned about how events abroad have a way of upsetting our assumptions about U.S. politics.

During the last year, Paul’s stock has risen within Republican circles as concerns over U.S. spying tactics, drone attacks and government scandals have propelled the libertarian into what might be considered the front runner’s spot for the 2016 GOP presidential nomination. While Paul’s strong performance in his drone filibuster and clever distancing of himself from his father’s extremism has enabled him to expand his libertarian base, this was only made possible by the complete absence of a debate on foreign policy among Republicans. Where once support for a strong defense and a robust U.S. presence abroad was mainstream GOP thinking, war weariness after Iraq and Afghanistan and cynicism about President Obama has made Paul’s neo-isolationism to become acceptable and perhaps even popular on the right.

But Putin’s seizure of the Crimea is forcing Republicans as well as the administration to think seriously about foreign policy in a way they haven’t for years. In response, some on both the right and the left are responding by asking why the fate of the Ukraine should interest Americans. While they may sympathize with Putin’s victims, they say the question of sovereignty over Crimea or even the possible reconstruction of the old Soviet empire by the new Tsar in the Kremlin has nothing to do with American security or our interests. Though they self-consciously avoid echoing Neville Chamberlain’s characterization of Czechoslovakia in 1938 after Munich as a “faraway country” when distancing themselves from Ukraine’s peril, there’s little question that they are just as willing to have the West abandon it as it did the Czechs. But such thinking is not only callous; it is irresponsible. Ukraine can only be ignored at the cost of America’s credibility as a world power and to the detriment of the cause of liberty that people like Paul claim to support.

Obama’s fecklessness on Syria, Iran and now Ukraine have made the world a much more dangerous place. Unless you are prepared to retreat back to fortress America, a planet where tyrants feel free to act against U.S. allies and friends is one in which the U.S. is reduced to a second-rate nation with no power to protect its interests or its friends. We’ve already started to see that happen in the Middle East where both Israelis and Arabs now have good reason to be afraid of Iran, and in Europe where Putin is demonstrating that Western-oriented democracies can now be subjected to aggression with impunity. If history teaches us anything it is that such a situation is one in which the U.S. must demonstrate strength or watch as thugs like Putin misinterpret American apathy for a license to do as they like. That often creates unintended consequences for those who think they can ignore the world. To allow the Russians to lie about the Ukrainian protesters who deposed Putin’s puppet regime and to call them Nazis is highly ironic when it is Moscow that is committing aggression in a manner that is highly reminiscent of Europe’s tragic past.

Ron Paul and the libertarian core never demonstrated much interest in pushing back against foreign tyrants because they share the far left’s belief that it is U.S. “imperialism” that is primarily to blame for foreign strife. Rand Paul has benefited from the support from such people but now seeks to have it both ways and convince mainstream Republicans that he can be trusted to defend U.S. security. But there’s no defending American interests or a stable international order while the U.S. full retreat. Just as George W. Bush’s less than robust response to Russia’s 2008 invasion of Georgia set the stage for today’s events in the Ukraine, a weak performance by President Obama could mean that Putin’s next victims could be NATO members in the Baltic republics.

Republicans who claim to value freedom above all values should be capable of understanding that isolationism means treating that word as irrelevant to U.S. foreign policy. Conservatives who remember that concern for the fate of the enslaved people of the Soviet empire was a core principle for Ronald Reagan’s GOP cannot abandon the same people now with a clean conscience. The United States isn’t France. It is the sole superpower democracy and when it abandons its principles abroad the world has a tendency to unravel. That not only hurts the U.S. economy. It will also involve us in conflicts that are not yet on our radar and we won’t be able to ignore no matter how much we’d like to. The return of foreign policy to the front burner of American politics should be the beginning of a process that returns Paul’s libertarians to the margins of American politics.