IT'S ALMOST hard to remember at this stage, but just after the Chris Christie bridge scandal broke, pundits quickly denounced it as as the kind of "nakedly partisan score-settling" that could destroy Mr Christie's carefully constructed bipartisan reputation. But as Timothy Noah quickly pointed out, and Jon Chait reiterates today, this got things exactly wrong: the scandal wasn't an example of excessive partisanship, but of a particular kind of bare-knuckles bipartisanship. It is still not entirely clear exactly what Mr Christie's staff was trying to achieve by ordering the lanes closed, and by now we've all moved on to claims by the mayor of Hoboken that Mr Christie threatened to short-change her city on federal relief for damage from Hurricane Sandy if she didn't endorse him. But whatever the details turn out to be, the big picture is that Mr Christie is getting in trouble for the hardball measures he used to build the bipartisan support that he needed to govern as the Republican leader of a largely Democratic state. Americans profess to love bipartisanship, but rarely think about what it takes to generate it. Politicians don't cooperate with each other because they have similar tastes in music. If they don't belong to the same party or faction, they are only likely to cooperate if it will bring them or their constituents some sort of benefit. The rise of partisanship in America has made this sort of collaboration vanishingly rare. Politicians who make deals across party lines, especially on the Republican side, are now easy targets for primary challenges by candidates who accuse them of betraying the party and its ideology. Chris Christie was one of the few Republicans in the past decade to buck this trend, offering political support to Barack Obama in exchange for a highly public role in the distribution of federal disaster-relief benefits after Hurricane Sandy. He wanted the same sort of political support from Democrats; in many cases he received it, but not from the Democratic mayors of Fort Lee and Hoboken. Mr Christie's administration is now being accused of retaliating against both those cities.

The key to the bridge-closing scandal is that the measures Mr Christie's administration took were so punitive. Instead of punishing opposing-party politicians for withholding their endorsements, he could have tried rewarding them for endorsing him. And to some extent, it seems he did; Loretta Weinberg, the Democratic majority leader of the state Senate (who, perhaps not coincidentally, also represents Fort Lee), told TalkingPointsMemo's Hunter Walker in December that Mr Christie had rewarded Democrats who endorsed him with state grant money and judgeships. But accusations that Mr Christie was trading favours for support didn't touch off a scandal. The scandal blew up when it turned out that officials had actively damaged the quality of public services by causing traffic jams. Had Mr Christie offered to build Fort Lee a couple of new on-ramps to the George Washington Bridge after receiving an endorsement, political junkies might have chuckled a bit, and that would have been about it. Mr Christie could have strewn budgetary gifts from Ridgewood to Cape May in exchange for cross-party endorsements and never suffered more than a few raised eyebrows.

But Mr Christie had a very limited supply of such budget goodies to hand out. Why? Because he’s Chris Christie! He’s a Republican governor who has made his reputation by slashing New Jersey’s budget. His party has spent 30 years locking itself into an ever-more-rigid ideological commitment to shrinking the size of government. So Republicans have almost nothing in the way of positive inducements to get Democrats to collaborate these days. At the national level, the last time Republicans could win bipartisan support by offering something positive was a decade ago, when George W. Bush secured Democratic backing for new government initiatives such as Medicare Part D and No Child Left Behind. Mr Bush is now a figure of contempt among conservatives precisely because of his deficit-spending habits, and it's hard to imagine that model being repeated. Mr Christie himself famously killed a multibillion-dollar public infrastructure programme that would have lessened traffic over the George Washington Bridge. Indeed, the biggest new item on Mr Christie's 2014 budget bill is a $2.3 billion tax cut for businesses. So what he's left with are negative inducements, like threatening to cause traffic jams, or threatening to withhold free disaster aid from the federal government. Mr Christie didn't have any candy to dish out, so he had to deliver thumpings instead.

It is ridiculous for voters to expect politicians to cooperate across the aisle without giving them any reason to do so. David Plotz, arguing in America's pre-eminent journal of counterintuitivism, explains why America needs more of Mr Christie's brand of politics. He pointed to the disappearance of earmarks: after the 2010 Republican landslide, Congress eliminated the old system in which members could target a small amount of the budget to specific programmes in their own districts. (This was partly owing to the efforts of Tom Coburn, a Senator from Oklahoma, who announced his retirement this week.) Since then, Congress has been hamstrung. Last week, for the first time in years, an omnibus appropriations bill passed with overwhelming bipartisan support, and one of the reasons, as Stan Collender pointed out, was that it "provided an opportunity for the leadership to buy support from reluctant members by providing more dollars for their pet programs and projects... This was the first appropriations bill in five years where that wasn't the case."

There are always options for public spending that are more or less deserving; allowing the legislative vote market to shape how some of that spending is prioritised is not an absurd idea. More broadly, there are trade-offs for everything. If we don't let politicians trade a little spending for support, we are left with either Mr Christie's punitive bipartisanship, or with pure partisanship, which we claim not to like either.