HEMPSTEAD, N.Y. – During tonight’s town hall debate here at Hofstra University, President Obama repeatedly called out Mitt Romney on his tax plan, arguing that the math didn’t add up. But in the spin room following the debate, Obama campaign press secretary Jen Psaki struggled to defend the math in the president’s own deficit plan.

Obama has repeatedly argued that he has a proposal to tackle the nation’s debt problem through a “balanced approach” that spares deep cuts to entitlement programs by raising taxes on the wealthiest Americans.

In the spin room following the debate, I noted to Psaki that Obama’s math has its own problems. He preserves roughly 80 percent of the Bush tax cuts in terms of revenue and the taxes he raises won’t be enough to balance the budget or save Medicare or Social Security from cuts.

“President Obama is the only one who has a $4 trillion balanced plan, so part of that is $1 trillion in ending the Bush tax cuts,” Psaki said.

In response, I noted the the supposed $4 trillion deficit plan included $1.1 trillion in war savings and $1.2 trillion from the debt ceiling compromise that had already been signed into law.

“I think the important piece is that Mitt Romney has a $5 trillion plan,” Psaki began to reply.

I pressed her on Obama’s own plan, that keeps 80 percent of the Bush tax cuts without tackling entitlements.

She said, “I think we’re talking about a couple different things. His plan is a $4 trillion plan. Part of it is ending the Bush tax cuts, part of it is making tough cuts to programs like Medicare and Medicaid. He’s happy to make tough cuts and he also wants to invest in education and other programs.”

I responded that the claimed mandatory savings were mostly offset by nearly $500 billion in new spending on his economic proposals.

“Yep,” she said. She told me, “I’m happy to send you a copy of the president’s plan outlined with all of the specifics of that.”

I reacted by saying that, “I’ve read it a lot of times and the specifics say $1.2 trillion is from the deficit reduction deal, $1.1 trillion of it comes from the war savings – the idea that you’re not going to be at surge levels in Iraq and Afghanistan in perpetuity – and then you have the Bush tax cuts on 20 percent of the people not getting extended and so that does not add up to, it does not balance the budget.”

(When I said “20 percent of the people” I should have been clearer, as I was earlier, that Obama was only scraping 20 percent of the Bush tax cuts in revenue terms.)

“That adds up to a down payment,” Psaki said. “The point here with the $5 trillion plan of Mitt Romney is not laid out at all how he would pay for it, has not laid out any specifics.”

I asked how it could be a down payment if it doesn’t balance the budget or change the long term trajectory of entitlements.

“It’s a $4 trillion down payment,” she shot back, and then turned to another question.