Don’t look now, but Mitch McConnell’s plan to transfer ownership of the debt ceiling to the President has quietly gained serious legitimacy among top Democrats. They now see it as an active plan B.

“Some version of it is definitely the plan B if these larger discussions don’t pan out,” a senior Senate Democratic aide tells me.

Democrats see McConnell’s proposal as a key opening, largely because it constitutes an acknowledgment on McConnell’s part that the debt ceiling must be lifted — a display of urgency that from the point of view of Dems has been alarmingly lacking in other Republicans.

“We are relieved that at least someone on the GOP side says that if nothing else happens, the debt ceiling still needs to be lifted,” the aide continues. “Here you have McConnell siding with Democrats on the urgency of the situation.”

What form will the McConnell proposal take? Sam Stein reports that Harry Reid and Mitch McConnell’s offices are in discussions over ways of packaging over $1.5 trillion in spending cuts with the McConnell proposal. The idea would be to make it an easier sell with conservatives, presumably making it easier to pass through the House. A Dem official described the idea as a “hybrid approach.”

The key question remains: Can this pass the House? It would need the support of House Republicans and Dems. We already nkow conservatives oppose it. But Dems might also balk, because the package as envisioned would only contain spending cuts and no revenue hikes. Steny Hoyer has said Dems can’t support any final deal without increased revenues. As best as I can determine, House Dem leaders have not tried to gauge whether the current McConnell proposal could earn Dem support. But Dems could end up supporting it, because presumably the spending cuts packaged with the McConnell proposal wouldn’t be entitlements cuts, and Dems could then say they emerged with a deal that keeps their sacrosanct programs intact.

As for whether enough House GOPers could support it, today John Boehner said he didn’t know whether the McConnell proposal could pass the House. But the bottom line is that this route could end up being the best endgame possible for House Republicans, who are now backed into a corner. Under the McConnell proposal, House GOPers would have secured spending cuts and given up no revenue increases. Not only that, but they’d be able to repeatedly vote against the debt ceiling hike — without having to worry about it actually preventing the hike from happening! That’s because under the McConnell proposal, the House can vote to disapprove of the debt ceiling hike, but the president can veto that vote. Without a veto proof majority disapproving, the debt limit would be lifted despite the GOP’s votes against it — keeping business leaders happy and preventing an implosion of the economy and a political disaster for Republicans. A win win!

So some form of this proposal may still prove to be the way out in the end.