With the GOP threatening to trigger a government shutdown or debt default over ObamaCare, the White House is trying out a new argument to sway voters: Republicans are nuts.

In a speech this week defending the health care law, President Obama chided Republicans for their dire threats about the Affordable Care Act, accusing them of trying to "blackmail a president" and of "poisoning" the law.

He then specifically cited wild criticisms of the law, including a GOP lawmaker's claim it was "as destructive to personal, individual liberty as the Fugitive Slave Act," and Rep. Michele Bachmann's (R-Minn.) warning that the law had to be stopped before it "literally kills women, kills children, kills senior citizens."

"All this would be funny if it wasn't so crazy," a visibly exasperated Obama said.

On the same day, senior White House adviser Dan Pfeiffer compared GOP lawmakers to nihilistic suicide bombers, citing their willingness to push the U.S. economy over a cliff to stop ObamaCare.

"What we're not for is negotiating with people with a bomb strapped to their chest," he told CNN, adding that "it's not a negotiation if I show up at your house and say give me everything inside or I'm going to burn it down."

On Twitter, Republican National Senatorial Committee spokesman Brad Dayspring wondered if Pfeiffer had screwed up.

Yet the harsh language is most likely deliberate, an attempt to paint Republicans as unhinged and unreasonable ahead of a coming showdown. With increased pressure from voters, the administration hopes cooler heads in the Republican Party will see the folly of brinksmanship. And if a debt default or shutdown were to occur, the White House is making sure the public backlash falls squarely on the GOP, not the president.

Republicans are giving Obama plenty of ammo for his "crazy" charge.

The possibility of a government shutdown, which appeared to be waning earlier this week, roared back on Thursday. House Republicans said they would not accept a budget bill stripped of language defunding ObamaCare, which the Senate is expected to pass over the weekend.

Republicans on Thursday also outlined their initial demands for raising the debt ceiling. The list is festooned like a Christmas tree with GOP priorities, very few of which have anything to do with the budget. Indeed, some say the list is essentially Mitt Romney's economic platform, which was obviously rejected by voters last fall.

Though the requests are steep, they reflect the GOP's belief that the debt ceiling will offer a more advantageous bargaining position for them than the government shutdown fight. The move has bolstered the impression that the debt ceiling has become a tool for the GOP to bully the country into accepting its agenda, rather than a supposed bulwark against government spending. And it has also betrayed the GOP's willingness to invite economic calamity in order to get what the party wants.

A debt default could be catastrophic for the economy. And demanding that Democrats make all the concessions on a Christmas wish list of GOP priorities in exchange for not deliberately tanking the economy is not exactly sound governance.

"Perhaps Republicans feel that gives the threat of breaching the limit more leverage," Mark Zandi, of Moody's Analytics, told Politico. "Or perhaps some don't believe the impact of breaching the limit would be that bad. But to be frank, I'm as perplexed as you are."

President Obama has flatly said he will not negotiate on the debt ceiling precisely because of the damage it could do to the economic recovery. Republicans have seized on that, accusing him of being unreasonably recalcitrant.

If Obama is going to win the public opinion battle over the ObamaCare hostage crisis, he'll need to convince Americans that Republicans are actually the ones being unreasonable. If not, he could risk coming off as, well, crazy.