The Senate unanimously rejected President Obama’s budget yesterday, two months after the president’s budget was voted down unanimously in the House. It’s an embarrassing testimony to both Obama’s leadership and the Senate majority leadership’s willingness to take the long-term deficit problems seriously, particularly during an election year, and Democrats are furiously swinging into spin control mode.

The fallback excuse for Senate Democrats during the past few months has been that the debt ceiling deal already put spending caps into place, making a new budget unnecessary. They’re still standing by that claim:

Democrats say the exercise is unnecessary this year because Democrats and Republicans wrote spending caps for the year into law in the hard-fought summer deal that raised the nation’s debt ceiling.

Republicans counter that the debt deal does not replace a legal requirement that Congress adopt a budget resolution for the year.

It’s not just Republicans who are countering the claim. The Senate parliamentarian also ruled in April that the debt ceiling deal doesn’t mean the Senate can’t take up budget resolutions this year.

Meanwhile, the White House was expecting the failure, and recently began arguing that the resolution introduced in the Senate is actually a distorted version of the president’s budget. They say the rejection isn’t a reflection of Democrats’ views of Obama’s plan:

Last May, Obama’s budget was voted down, 0-97. Democrats noted they could vote no after Obama delivered an April speech calling for deeper deficit reduction than he had presented two months earlier in his budget.

This year, Obama is sticking by his budget, so Democrats are embracing another reason to vote it down.

The White House moved Monday to free Democrats to vote no by saying the legislation embodying Obama’s budget is “different” because it doesn’t contain identical policy language.

Republicans argue that the rejected budget resolution is identical to Obama’s plan, and say the only difference is that campaign-tinged political language was removed.

“If you look at the president’s budget it reads like his campaign website,” a Republican aide told me. “But the numbers are identical to the budget.”

The excuses are pretty flimsy, and Democrats are no doubt bracing for a public backlash. But clearly the party thinks they’re safer dealing with the fallout from rejecting Obama’s budget than being forced to defend his budget in the fall.