THE ostensible purpose of an election campaign debate is to give candidates a chance to share their views and attract possible voters. Political debates have a long tradition: in 1858 a lawyer named Abraham Lincoln challenged Senator Stephen Douglas for his seat in a series of seven debates in Illinois. One candidate would open with a 60 minute speech, and the other would give a 90-minute response. The first candidate would then close the debate with yet another 30 minute speech. Although Mr Lincoln went on to lose the Senate race, the debates elevated his national stature and set him up for a successful presidential run against Mr Douglas two years later. Most debates, however, have far less impact. Academic research suggests that although presidential debates can inform a person’s view, they tend to do little to change it. In their book “The Timeline of Presidential Elections”, political scientists Robert Erikson and Christopher Wlezien looked at every American election featuring televised debates between 1960 and 2008 and found that the polling numbers of presidential candidates leading up to debates were almost perfectly correlated with their polling numbers shortly afterwards. But most research looks at the later stages of elections, when parties’ candidates have been chosen. Debates almost certainly matter more during the primaries for two reasons: first, voters will almost never know who all the candidates in a presidential primary are, which means there is more scope for shaping their perceptions. Second, many voters are staunch partisans; it is far easier to convince someone to choose another candidate from their own party than to defect altogether.

It does seem that debates have had a big impact in shaping the outcome of primaries. In 2011's Republican presidential primary race, Rick Perry declared that he would shut down three wasteful government agencies if elected, but failed to recall the names of all three he had in mind. Mr Perry never recovered from his gaffe, and ended his campaign two months later. Earlier this year, in a debate just three days before the New Hampshire primary, Chris Christie attacked his rival Marco Rubio for repeating the same lines over and over again. Mr Rubio was caught off-guard and responded by robotically repeating the same line—yet again. The fallout was immediate: not only was Mr Rubio confronted by hecklers in robot costumes, he tanked at the ballot box, placing fifth in New Hampshire after being expected to finish second.

More than 157 years after the Lincoln-Douglas debates, the level of political discourse seems to have slipped. Though the Democratic debates have remained relatively civil this cycle, the Republican debates have devolved into schoolyard shouting matches. In a debate on February 25th, the television subtitles described one particularly heated segment as “unintelligible yelling”. During the most recent Republican debate, front-runner Donald Trump christened his two chief rivals “Little Marco” and “Lyin’ Ted” and assured viewers that there was “no problem” with his manhood. It’s not always clear exactly what informational value voters will be able to extract from some of these debates, but they do at least make entertaining television.