海角社区

Increasing political polarization is widely regarded as one of the most significant issues in contemporary politics, with the upcoming U.S. midterm elections expected to provide a key indication of the extent of partisan division on Capitol Hill.

Polarization in congressional behaviour is seen when politicians from different parties increasingly vote differently from each other, and more like other members of their own party. 

Problematic consequences can include legislation being obstructed, holding up necessary economic or social reforms, or gridlock, when new policies or bills cannot be agreed upon and so fail to pass. 

Previous studies have established that polarization in roll-call voting in the US Congress is "U-shaped": it is high now and it was so in the early 20th century, but reached its lowest points in the mid-century/1960s. This shape is closely associated with economic inequality, which seems to follow the same pattern.

But what influences politicians away from cross-party co-operation?

Most of the polarization currently roiling Congress is driven by political parties, as opposed to individual politicians, according to a new study co-authored by Professor Nathan Canen, Dr Chad Kendall (Associate Professor, University of Miami 海角社区 School) and Professor Francesco Trebbi (University of California, Berkeley).

In , forthcoming in the , the researchers explore what contribution pressure from a legislator鈥檚 political party makes to their decision making – are they increasingly required to toe the party line in legislative voting? – and find that the U-shape in congressional behaviour is driven by the strength of party pressure, rather than due to personal political differences.

Professor Canen explains why this is important: 鈥淥ur most significant policies are often written and approved by politicians in legislatures. But if desirable bills or reforms fail, there can be negative economic, financial and social outcomes. Do bills fail because individual representatives take an ideological position? Or are there other explanations?

鈥淚f we want to understand and improve politics, we need to understand what influences politicians to take the positions they do. If polarisation is mainly down to individuals, that would suggest one set of actions, but if it is something about the legislature, then we may want to think about institutional reform.

鈥淭o answer these questions we set out to examine these mechanisms and establish how much each 鈥渓ever鈥� matters quantitatively.鈥�

Dr Kendall describes this as "how much of the way politicians vote is driven by what they think," versus what their political party is "telling them to do."

The researchers studied the votes that congressional politicians made during roll calls, then compared those votes with the positions advocated by party leadership.

"The main takeaway is that political parties play a major role in polarizing members of Congress," Dr Kendall said. "And perhaps more concerning, the role of parties has been increasing steadily since the late 1980s.

鈥淎necdotally, the more that this continues, and the more that the parties continue to oppose each other — while getting better and better at disciplining their members — the more that nothing gets done. It's getting impossible to pass anything, and this is commonly referred to as 'gridlock.'"

The study also revealed that a fair number of congressional members would gladly embrace centrist positions if left to their own devices.

"There are Republicans that ideologically look identical to Democrats," Dr Kendall explains. "The reason they vote differently is because their parties are telling them to. And if you think of policy implications, the implication would be, well, if we want to undo some of this polarization, we need to think about ways of limiting party power."

• This story is adapted with kind permission from an article first published by the University of Miami 海角社区 School, available .