WASHINGTON -- In a much replayed moment from Thursday night's debate, Vice President Joe Biden and Rep. Paul Ryan tussled over whether it was mathematically possible for Mitt Romney to cut tax rates by 20 percent and not add to the deficit. Ryan claimed that it could be done by eliminating unspecified loopholes and deductions, and said that history had demonstrated that such a plan was workable, citing President John Kennedy.
Biden challenged him, arguing that no such thing had ever happened.
In a rare moment of bipartisan accord, Romney himself agrees with Biden's assertion.
"Let's look at history. My plan is not like anything that's been tried before," Romney said at last week's presidential debate.
Ryan argued Thursday that their tax plan is workable. "You can cut tax rates by 20 percent and still preserve important preferences for middle-income taxpayers," he said.
"Not mathematically possible," Biden responded.
"It is mathematically possible," Ryan said. "It's been done before. It's precisely what Republicans are saying ..."
"It has never been done before," Biden interjected.
"It's been done a couple of times," said Ryan.
"It has never been done before," said Biden.
"Jack Kennedy lowered tax rates and increased growth. Ronald Reagan ...," Ryan offered, before Biden cut him off to say, "Oh, now you're Jack Kennedy."
"This is amazing," Biden said.
"Republicans and Democrats have worked together on this. You know, I understand you guys aren't used to doing bipartisan deals," Ryan said.
Kennedy's tax cut did spark growth in the economy, but it's difficult to compare with Romney's plan without some sort of details from Romney or Ryan about what the plan actually is. Still, according to Romney, his plan has never been tried before.
Brendan Buck, a Ryan spokesman, said that the GOP vice presidential nominee was referring to bipartisanship when he said it's been done. "Ryan was talking about Republicans and Democrats working together to lower tax rates -- not the particular plan we've proposed," Buck said.
The exchange called to mind perhaps the most famous put-down in vice presidential debates, Lloyd Bentsen's 1988 line about Dan Quayle's lack of resemblance to Jack Kennedy.