It's the worst-kept secret in Washington that the Obama campaign and liberal Super Pacs are set to dust off those "Mediscare" TV ads showing Paul Ryan tossing grandma over the cliff. These attack campaigns are designed to undermine Republican plans to curtail the stampeding costs of Medicare. The ads have worked for Democrats in the past. It first started back in 1995 during the Newt Gingrich era when President Bill Clinton stymied GOP budget balancing plans.

The Romney campaign understands the vulnerability and is strategizing a counteroffensive. "This is going to be the lowest, meanest campaign in history," predicted Mitt Romney yesterday. He challenged Mr. Obama to take the campaign "out of the gutter." Fat chance.

One of the characteristics that Mr. Romney found attractive about Mr. Ryan is that he has never ducked from the crisis of the runaway train of entitlements. By 2014 the Medicare system runs out of money, according to the program trustees. "Doing nothing is not an option if we care about seniors," Mr. Ryan says. One fiscal fact that the Obama campaign wants to keep hidden from view: Today Medicare costs just over "500 billion. Under the Ryan "cuts" the program will cost over $800 billion by 2024.

He's got the facts and the math on his side (as even Mr. Obama has admitted about the entitlement fiscal time bomb) but that might not be enough.

Click for Stephen Moore's complete column in The Wall Street Journal