As lawmakers begin their August recess, the airwaves back home are filled with ads arguing all sides of the healthcare debate. But one commercial stands out. Two liberal interest groups are attacking Sen. Ben Nelson of Nebraska as a tool of the insurance industry.

Nelson is a Democrat, but in the eyes of the liberals, he’s also a heretic. He’s committed the sin of moderation by opposing a “public option” to compete with private sellers in the insurance marketplace.

The folks who finance these two pressure groups – Democracy for America and the Progressive Change Campaign Committee – should ask for their money back. It’s being spent, to use a current Washington buzzword, “stupidly.”

Nelson has not won four statewide elections by misreading Nebraska voters. A card-carrying moderate, he’s the only kind of Democrat with a chance of winning that deep-red state (John McCain thrashed Barack Obama there, 57 percent to 42 percent). In fact, getting attacked by out-of-state liberals is a badge of honor. The TV ads are a total waste of money – except to reinforce Nelson’s down-home credentials.

Nelson is a “majority maker,” a favorite phrase of House Speaker Nancy Pelosi. Without centrists like him, the Democrats could not control either house of Congress. And that hard truth leaves them with a stark choice on healthcare legislation.