By any metric — military spending, number of worldwide bases and alliances, quality of technology — America's military is by far the world's most powerful. Yet the majority of Americans don't see it that way. In a Gallup poll released in February, only 49 percent of Americans said that the US had the strongest military in the world. That was the first time ever that a Gallup poll has found less than a majority saying America wasn't the world's strongest power.

Since 1993, Gallup has asked Americans whether "America is number one in the world, militarily" or whether "it is one of several leading powers." This year is the first when the two results were tied, though it's been close before:

This finding makes the Republican strategy on foreign policy make a whole lot more sense. For virtually the entire election cycle, Trump has been blaming Obama for torpedoing America's strategic position, hollowing out its military, and making the world a more dangerous place.

They're picking up on a real vulnerability. Two-thirds of Americans, according to Gallup, think America should be number one, and not just "among the leading powers." Many Americans who think their country is now just one great power among several aren't happy about it, and some blame Obama and the Democratic candidates who largely back his foreign policy.

There is, no doubt, a bit of a cycle here: The more Republican candidates talk about America's military weakness, the more Americans (especially Republican partisans) come to believe that US military strength has declined.

But the bigger question is why Americans' faith in the country's military strength appears to have weakened even before the 2016 campaign began.

The broader trend: US weaker under Democrats, stronger under George W. Bush

These changes don't reflect shifts in America's actual strategic position: Since the end of the Cold War, America has unquestionably been the world's strongest power, with no country even approaching peer status. Rather, public attitudes likely reflect the past three presidents' approach to the military, in terms of both rhetoric and actual policy.

There are basically two trends in the above chart. Bill Clinton and Barack Obama started out their presidencies with polls showing strong American belief in US military primacy, which then declined. Under George W. Bush, it was the opposite: Americans became more confident in US military dominance as his presidency continued.

Bush's foreign policy was practically centered on the idea that the US military, properly deployed, could transform the world — eliminate terrorism, topple rogue regimes, and turn Iraq's dictatorship into a democracy.

Clinton and Obama, by contrast, were both far more hesitant about starting major wars — and thus, rhetorically, less prone to playing up the ability of the US military to fundamentally change the world. Obama especially has emphasized the limits of American power to solve problems like ISIS, even in the face of widespread public fear about the group.

Americans pick up on this. They interpret "the US military can't solve all problems" as "America is losing its military edge," and thus start seeing America as just one great power among many.

Hence, American strength is perceived to be lower under Clinton and Obama than Bush, and even lower under Obama than Clinton. Americans are overreacting to what their presidents say and do, and ignoring the fundamental reality behind the headlines in the process.