 -- A top advisor to President Barack Obama urged Congressional Democrats on Friday to "go on offense" against Republicans on the issue of taxes and argued that the Supreme Court ruling upholding the incumbent's signature health care law should be the "clear and final" word on the issue.

In a memo made public by the White House, David Plouffe accused Republicans of "trying to misrepresent" Obama's record on taxes.

"We welcome this debate on middle class taxes, and we urge you to seize this opportunity to go on offense to illustrate how the President and Democrats in Congress are standing up for the middle class," Plouffe wrote.

The issue has flared up in part because the Court upheld the individual mandate on grounds that it amounted to a tax — a ruling Republicans pounced on to accuse the president of trying to enact a stealth tax hike.

"Yesterday, the court blew the president's cover," said Republican Senate Minority Leader Mitch McConnell. McConnell noted that Obama had repeatedly denied that the individual mandate — which requires Americans to have insurance or pay a fine — amounted to a tax. "The reason was obvious: if Americans knew that failure to comply resulted in a tax hike, it never would have passed," McConnell said. "And the President wouldn't be able to claim his health care bill didn't raise taxes on the middle class, as he did, again, and again, and again."

McConnell said that at least 77 percent of the people who stand to pay what the White House doggedly describes as a "penalty" meet the president's definition of "middle class." The White House has said that just 1% of Americans will be affected, describing them as "irresponsible" folks whose choice not to buy insurance shifts their health care costs to everyone else. The law only targets those who can afford to buy insurance but do not.

But White House officials plainly see the political danger in Obama being portrayed as a tax hiker. Asked about Plouffe's memo, a senior Republican congressional aide told Yahoo News: "This is amusing. As the kids say: nervous much?"

Plouffe's message listed talking points to blunt the tax hike threat. These include the argument that Obama "has cut taxes by $3,600 for the typical middle class family." And it highlights that, under Obamacare, roughly 18 million middle class individuals and families will get a tax cut averaging $4,000. On the issue of what Republicans (and Chief Justice John Roberts) are calling the individual mandate tax, Plouffe's memo says it was "modeled" on Mitt Romney's overhaul of Massachusetts health care when he was governor.

The court ruling on Thursday disappointed and even angered conservatives, but Romney stands to reap a political benefit from core Republicans' loathing for the law. His campaign has left no doubt that vows to repeal Obamacare will be a campaign trail staple.

"The bottom line is this though: the Court has issued a clear and final ruling on this law," Plouffe said. "The last thing Congress should do is refight old political battles."

"As we implement this law, we should improve it where we can and give States more flexibility," he wrote. "Right now, Congress needs to work together to focus on the economy and creating jobs."