Attorney General Martha Coakley has been catching flack today for flubbing the amount of the Massachusetts gas tax during an appearance on WCVB’s On the Record over the weekend. Coakley said she thought the state’s gas tax was 10 cents per gallon; the actual amount is 24 cents per gallon.

Coakley’s error is certainly more understandable than when she called Curt Schilling a New York Yankee. In fairness to the Attorney General, and in contrast to the Schilling gaffe, she is not alone in her error on this question. When we asked Massachusetts residents how much they thought they paid in federal and state gas taxes combined, almost no one got the right answer. Less than 1 percent of all respondents got within a penny of correct amount (41.9 cents, at the time). Almost one in five (18 percent) guessed lower, as Coakley did, and 31 percent didn’t offer a guess. But over half (52 percent) overshot the mark. Three in ten thought we pay more than a dollar in taxes for every gallon of gas; 12 percent thought they were paying was more than $2. To put these guesses in perspective, according to AAA, the average national price of gas in February 2013, when the poll was taken, was $3.65.

Q: If you had to guess, how much of the cost of every gallon of gasoline in Massachusetts would you say goes to federal and state taxes?

Guessed less than $0.41 18%
Guessed $0.41 to $0.42 <1%
Guessed $0.43 to $0.99 21%
Guessed $1.00 to $1.99 19%
Guessed more than $2.00 12%
Don’t Know / Refused 31%

These overestimates of the gas tax may have a real impact on the likely ballot question to repeal the indexing of the state gas tax to inflation. About half the population (52 percent) perceives a higher gas tax burden than actually exists, meaning they perceive a higher baseline to which any new tax on gasoline would be added. Thus, a “tax relief” narrative will arguably be more effective than it would be if everyone knew the actual amount of the tax in question.

With both sides gearing up for a fight over gas tax indexing in November, it’s likely that candidates and voters alike will be getting much more familiar with what we’re paying now and what we may be paying in the future.