Rep. Paul Ryan’s budget briefly had a Democrat’s support. (Michael Reynolds/EPA)

Make that one lonely Democratic “yes” vote.

On the budget that Democratic leaders have called a Medicare-slashing, Big-Oil-subsidizing horror-show? That was a surprise.

Alas, for Republicans who no doubt would have liked to call their plan “bipartisan,” the sole Dem vote disappeared from the “yes” column before the vote was gavelled to a close.

The final tally was 221-207, with zero Democrats voting for the proposal.

It’s entirely likely that a Democrat accidentally voted in favor, then realized his or her error and switched it. That’s not uncommon. What with all the votes members have to keep straight, and clumsiness when using that vote-card machine (swipe of a card, then hit a red button for no, green for yes, and yellow for present) mistakes can happen. Or, perhaps, the “yes” vote had a very rapid change of heart.

We don’t know. And a spokeswoman for the Democratic whip’s office didn’t immediately return our call looking to identify the vote-flipper.

As it turns out, 10 Republicans voted against the bill — and we can only assume those votes weren’t mistakes — meaning there was bipartisan opposition. But the bipartisan support was merely fleeting.