President Barack Obama lashed out defiantly and viciously at political opponents who defeated his efforts to expand federal gun regulations today. Standing with families of victims of the Newtown school shooting at the White House, the president claimed that opponents of expanded federal background checks had “no coherent arguments” for their position, and that the “gun lobby” had “willfully lied” in the course of the debate.

Ironically, while accusing others of lying, President Obama resorted to false claims and statistics about current laws, including the repeatedly debunked argument that 40% of gun sales are private, and that guns can be bought over the Internet without background checks. It was partly the dishonesty of those very arguments that had led potential supporters of new bipartisan legislation to doubt the administration’s motives in supporting the bill.

The administration’s defeat came earlier Wednesday, when the Senate failed to pass a cloture motion to end debate on a bipartisan proposal introduced by Sens. Joe Manchin (D-WV) and Pat Toomey (R-PA). Only 54 votes of the necessary 60 votes could be found to support an expanded federal background check system (among other changes), partly because of fears that extending such checks would require the creation of a federal gun registry that could lead to confiscation.

The failure brought an end to four months of fervent campaigning by the president during which he used the Newtown disaster–or, in the eyes of many critics, exploited it–to make an argument about the urgent need for new laws, even if such laws would not have prevented the Newtown atrocity itself. Many Democrats rallied behind him, hoping at first to pass a new assault weapons ban, then abandoning that effort for more modest regulations.

Along the way, the administration lost the support of Democratic Senators in conservative states, many of whom will face re-election in 2014. President Obama made clear his intention to use Wednesday’s defeat to rally supporters against Republicans, whom he blamed directly and angrily, suggesting that they had defied the will of the American people and attempted to silence the families of Newtown victims who had a “right” to be heard in the debate.

Forced to cover a rare political defeat for the president, the mainstream media largely echoed his emotions. Virtually all of CNN’s correspondents agreed that the Manchin-Toomey bill had been defeated because of the power of the National Rifle Association and the fear of politicians afraid to take on Second Amendment activists. None considered that support for gun control has been declining, or that the legislation itself was deeply flawed.

Again and again, President Obama noted that 90% of Americans, and a majority of National Rifle Association members, supported expanded background checks. The former constitutional law lecturer seemed to expect that that majority’s will should be self-executing, ignoring the fact that constitutional rights like the Second Amendment exist precisely to protect minorities against majoritarian passions and presidential demagoguery.

Indeed, while the president described the failure of the legislation as a failure of “Washington,” it was also–and primarily–a failure of his administration. A White House operation and Obama campaign apparatus that is regarded as brutally effective ought to have been able to sell a proposal allegedly supported by 90% of the voting public. Yet persistent troubles in execution and failures of policy raise questions about whether Obama secretly preferred failure to success.

His opponents, the president insisted, refused to make it more difficult for “dangerous criminals” to buy weapons–ignoring one of the core arguments of the other side, namely that dangerous criminals frequently ignore the law to obtain weapons, while law-abiding citizens bear the burden of new rules and restrictions. He reduced his opponents’ motives to pure politics, accusing them of being afraid of being punished by an organized, determined minority.

Rarely have Americans ever seen a president attack his opponents so viciously, expressing and evoking such visceral emotions–especially at a time of mourning. President Obama’s tirade contrasted with his reserved, measured response to the Boston Marathon bombings, in which he urged Americans to speak and act with restraint. If this has been, as he claimed, “a pretty shameful day in Washington,” the president’s tantrum was the most shameful moment of all.