“Obamacare cuts Medicare — cuts Medicare — by approximately $500 billion,” Mr. Romney has told audiences.

That is a reprise of Republicans’ mantra of the 2010 midterm elections, which gave them big gains at both the state and federal levels and a majority in the House. Yet the message conflicts not only with their past complaint that Democrats opposed reining in Medicare spending, but also with the fact that House Republicans have voted twice since 2010 for the same 10-year, $500 billion savings in supporting Mr. Ryan’s annual budgets.

The result is a messaging mess, even by the standards of each party’s usual election-year attacks that the other is being insufficiently supportive of older people’s benefits…

“A pox on both their houses,” said Ron Haskins, a former Congressional staff member who is now a scholar of social programs and budgeting at the Brookings Institution. Democrats and Republicans “know they have to do something about Medicare, and then they harass each other about cutting Medicare. It’s so discouraging to me, but I’m a Republican, so I’m much more distraught about Republicans.”