Does Paul Ryan’s own budget proposal give away the game on the debt ceiling — and undercut the GOP’s leverage on the issue — by acknowledging that it must be raised?

That’s what Democrats are now charging — and they are pointing to it as proof that Republicans have no leg to stand on as they hold out against the debt ceiling hike that everyone knows has to happen.

This has gotten little attention, but Senate Dems points out that on pages five and six of Ryan’s proposal, the plan lays out its version of what constitutes “appropriate levels of the public debt” over the next ten years. It says that in fiscal year 2012, the appropriate debt limit would be $16.2 trillion — nearly two trillion higher than it is now. In 2021, according to Ryan’s proposal, the proper debt limit would be $23.1 trillion — nearly $9 trillion higher than the present.

The Los Angeles Times noted the provision in a little-noticed blog post late Friday after the Ryan bill passed the House, asking: “Do House Republicans realize they just endorsed a higher debt limit?”

Dems are seizing on this to argue that Republicans supported raising the debt ceiling in their own plan — acknowledging that it has to go up no matter what. Brian Fallon, a spokesman for Chuck Schumer, emails:

“Despite their threats to bring the U.S. to the brink of default, the House Republicans’ dirty little secret on the debt ceiling is that they already voted to raise it just last week. Not only did the Ryan budget call for a higher debt ceiling, it spelled out exactly how much higher it should go — $2 trillion in the next year, and almost $9 trillion in the next decade.”

A House GOP budget spokesman didn’t immediately return an email for comment.

In fairness to Republicans, they can point out that putting a debt ceiling hike in the Ryan proposal along with entitlement changes and other proposals to reduce spending dovetails with the GOP’s public position, which is that Republicans will support raising the debt ceiling as long as it’s packaged with major fiscal reforms.

But Dems will counter that both sides have already agreed that borrowing needs to come down by around $4 trillion — meaning both sides agree that in a larger sense, the debt ceiling hike will be accompanied by moves to rein in the deficit, even if big differences remain over the details. Dems will argue that the GOP’s inclusion of a debt ceiling hike in their own proposal shows they know it has to happen — so the GOP should stop politicizing the issue.

Expect Dems to press this case in the days ahead.