THE EXISTENCE — and, until recently, the rapid proliferation — of congressional earmarks presents a quandary. Lawmakers have a legitimate interest in securing funding for their districts. The Constitution grants Congress the power of the purse, and earmarks reflect the exercise of that authority. On the other hand, the explosion of earmarked spending threatens to elevate political clout over the merits of a project. The existence of earmarks may not increase overall spending, but they may send limited dollars to where they’re not most needed. When bridges are crumbling, the country cannot afford bridges to nowhere.

That background is helpful in assessing the significance of the latest installment of The Post’s series “Capitol Assets.” Reporters Scott Higham, Kimberly Kindy and David S. Fallis scoured disclosure reports and public records and found 33 lawmakers who had steered more than $300 million in earmarks or other spending to projects located within two miles of properties they own. Equally, if not more troubling, the investigation identified 16 lawmakers who have taken actions benefiting entities connected to their immediate families. The importance of these findings is not necessarily that they demonstrate out-and-out corruption as that they illustrate the inevitable ethical questions intertwined with congressional earmarking.

The report also highlights gaps in current disclosure rules. Currently, and most likely for good reason after the tragic shooting of former representative Gabrielle Giffords (D-Ariz.), lawmakers do not have to provide their home addresses on financial disclosure forms. But certainly it would be reasonable, when lawmakers seek earmarks, to require that they disclose any nearby property holdings or the involvement of family members in the entity receiving the money — not merely to offer blanket certifications that they stand to reap no financial reward.

Consider the case of Rep. Bennie Thompson (D-Miss.), who obtained a $900,000 earmark to resurface about two dozen roads in his state — including a quarter-mile residential loop on which he owns a home. Mr. Thompson said he did not ask for his street to be paved; the local mayor, who described Mr. Thompson as a close friend, said the congressman “didn’t have anything to do with where the asphalt went.” But constituents can’t be blamed for wondering if Mr. Thompson, having secured the money for repaving, received preferential treatment.

The findings about lawmakers’ relatives working for institutions that benefit from congressional largesse were particularly disturbing. Rep. Ed Pastor (D-Ariz.) obtained a $1 million grant for at-risk high school students four years before his daughter was hired as its director, and earmarked $4 million more for the program since.

Mr. Pastor said he did not realize that his daughter was applying for the job. If he had, Mr. Pastor told The Post, “I would have contacted the chancellor and said, ‘What kind of position does that put you and me in?’ ” Which is, of course, exactly the question that lawmakers and voters, after reading this series, ought to be asking about the entire earmarking practice.