Public concern about America’s debt load tends to wax and wane, but it never really goes away. Recently, Reince Priebus, the chairman of the Republican National Committee, brought up the national debt again, right around the time the broadest measure of national debt broke through the $18 trillion barrier for the first time.

On Dec. 2, 2014, Priebus said that President Barack Obama has "the worst record of any president when it comes to putting America deeper in debt," according to an account in The Hill newspaper. He went on to call the growth in debt "immoral" and said voters had "tired of Democrats’ free-spending ways."

We wondered how accurate it was for Priebus to describe Obama as having "the worst record of any president when it comes to putting America deeper in debt." (While the Obama administration has touted its success in helping shrink the annual federal deficit , Priebus was clearly referencing debt, not the deficit , even though the two are obviously related.)

When we checked with the RNC, spokeswoman Kirsten Kukowski said the gross federal debt -- the amount of debt held by the public plus the amount of debt held by government entities -- had risen from $10.6 trillion to about $18 trillion during Obama’s time in office, making it the largest increase in raw dollars during any presidency.

Meanwhile, she added, the subset of debt that’s held by the public has more than doubled under Obama.

When we looked into these numbers, they checked out. However, given the snowballing effect of inflation and debt accumulation, it’s not surprising that whoever the most recent president is -- Republican or Democrat -- would experience the biggest increases in raw dollars of debt. So we looked at two other measurements that give a better sense of context for how much the debt climbed under Obama.

We used the Treasury Department’s daily database of federal debt, called Debt to the Penny , for data going back to 1993. For earlier presidencies, we used historical data from the Office of Management and Budget. We decided to use the broader measure of gross debt rather than the narrower measure of public debt -- even though both are valid measures of debt -- because for the past three presidents, data on gross debt is more consistently accessible. Meanwhile, to limit the impact of irregular presidential tenures, we looked at nine presidential periods of either four or eight years each: Eisenhower; Kennedy and Johnson combined; Nixon and Ford combined; Carter; Reagan; George H.W. Bush; Clinton; George W. Bush; and Obama. (We didn't go further back than Eisenhower because the high debt levels in the World War II era were a historical anomaly.)

Debt as a share of GDP

The first measure we looked at was growth in debt as a percentage of gross domestic product, or GDP. Experts say this is an important yardstick because it gives a sense of how burdensome the debt is on the economy. Smaller economies can sustain smaller debt loads; bigger ones can tolerate bigger debt loads.

Using this measure, Priebus has a point. The Obama years rank first -- that is to say, worst -- among the nine presidential tenures when measured by the increase in debt as a share of GDP.

At the end of fiscal year 2008, around the time Obama took office, gross federal debt accounted for 67.7 percent of GDP. The estimate for fiscal year 2014 is 103.2 percent. That’s a 35.5 percentage-point increase over six years -- far higher than any prior president we looked at, even those who served for a full eight years. (The end of fiscal 2008 was a few months before Obama took office -- a fact that has caused us headaches in the past -- but in this case, the gap is so wide that the discrepancy doesn’t make a significant difference.)

So big is the gap between Obama and the other presidents, in fact, that only three of the other eight tenures we studied saw any increase at all in debt as a share of GDP. Debt as a share of GDP went up by 18 percentage points under Reagan, by 12.3 points under George W. Bush, and by 11.7 percentage points under George H.W. Bush.

By contrast, every other president or combined presidential tenure saw a decline in the share of debt within GDP. Under Carter it went down by 2.6 points, under Nixon and Ford it fell by 5.9 points, under Clinton it fell by 6.8 points, under Kennedy and Johnson it was down by 13.3 points, and under Eisenhower it fell by 18.2 percentage points.

Percentage increase in debt from inauguration to end of tenure

However -- if you use a second measure, the numbers are more favorable toward Obama.

We looked at how much the gross debt grew from day one of the presidency to the end of that presidency, then adjusted for the length of time in office. On this list, the debt under Obama grew at the third-fastest pace -- and, awkwardly for Priebus, the two presidents under whom debt grew faster were both Republicans.

Reagan saw the biggest percentage increase in debt on his watch, at about 23 percent per year, followed by George H.W. Bush at about 13 percent per year and Obama at 11.5 percent per year. Those who saw slower debt growth than Obama were Carter (an increase of 11 percent a year), George W. Bush (10.8 percent a year), Nixon and Ford (8.8 percent a year), Clinton (4.6 percent per year), Kennedy and Johnson (3.3 percent per year), and Eisenhower (1.5 percent per year).

So, whether Obama ranks as "the worst" at debt accumulation depends on how you measure it.

Who gets the blame?

Another important factor to consider: How much is Obama responsible for this increase in debt?

Presidents do have an impact on the debt accrued during their tenure, but that impact is not all-encompassing. Presidents propose budgets and sign off, along with Congress, on final spending and revenue numbers. Programs they initiate cost money and, unless enough other spending is cut to produce a surplus, debt inevitably goes up.

In addition, debt tends to rise particularly quickly during recessions -- and Obama came into office with a doozy of a recession under way. In the debt per GDP measure, Obama was hit coming and going, since the numerator (debt) rose even as the denominator (GDP) fell during the recession.

"Certainly the Great Recession had a big impact" on debt accumulation under Obama, said Steve Ellis, vice president of Taxpayers for Common Sense. The recession, he said, meant both higher spending (on programs to aid the newly jobless and financially struggling) but also a loss in tax revenue (as once-employed Americans stopped earning wages they would have to pay taxes on). In addition, the Baby Boomer generation retired in increasing numbers under Obama, meaning both higher spending and fewer tax revenues.

"So it’s a mixed bag, and all presidents are a bit trapped by their time," Ellis said. "Did Reagan-Bush policies help create the surpluses experienced under Clinton? Republicans say so. Did the George W. Bush policies create the economic downturn that sent the debt soaring under Obama? Democrats say yes. Ultimately, all presidents are impacted by their predecessors’ policies and can be roiled by external forces."

This suggests that Obama bears some responsibility for the rise in debt, but hardly all.

Our ruling

Priebus said Obama has "the worst record of any president when it comes to putting America deeper in debt."

On Obama’s watch, debt as a share of GDP rose far faster than it did during any prior presidency. But if you look at the current amount of debt compared to where he started, the rise was not as fast as it was under Reagan and the elder Bush, two Republican predecessors. And while presidents bear some responsibility for debt accumulation, much of the equation -- economic and demographic changes and the consequences of prior president’s actions, in particular -- is out of their control.

The statement is partially accurate but leaves out important details, so we rate it Half True.