From now on, we’re not going to trust any numbers about the Medicare prescription drug benefit.

When the bill first passed in 2003, the White House promised to hold costs to $400 billion over 10 years. That was the price tag some budget-conscious members of Congress were demanding for their vote. It sounded great.

Once the bill passed – due largely to disregard for rules in the House of Representatives – the cost estimates ballooned to more than $530 billion, and we learned that the Bush administration had ordered its top Medicare expert to withhold information on the higher cost estimates of the plan from Congress. It should have been scandalous, but lawmakers let the slight, which might have been illegal, slip by with only ceremonial protest.

Now we learn that the prescription drug plan, which amounts to a major payday for the pharmaceutical industry, will really cost $1.2 trillion over a decade. But the administration promises that the real cost, after it massages some savings, will really be just $720 billion. Of course, that number could be baloney, too.

While the president aims to fiddle with Social Security, Medicare burns. The drug benefit is going to cost seniors more, provide less coverage than expected and still break the bank. Sen. Olympia Snowe has introduced legislation that would allow the government to negotiate with drug companies for lower prices. If the president wants to control the cost of his entitlement expansion, he’ll get behind the idea, which might at least trim the $1.2 trillion hole the benefit creates.

If he lets Snowe’s bill languish without support, we’ll know he doesn’t really care about cutting the deficit, providing affordable drugs to seniors or cutting the deficit.