In Scotland, long a Labour stronghold, the pro-independence Scottish National Party could take as many as 50 of the region’s 59 seats, which would block British Labour leader Ed Miliband from securing a majority. But Miliband, who has run a better campaign than his foes expected, could still end up in power, partly because Prime Minister David Cameron’s Conservatives are hemorrhaging votes to the UK Independence Party, which is critical of both immigration and the European Union.

In Greece, the traditional social democratic Pasok party was nearly destroyed after the country’s economic collapse. The left-wing Syriza party took power this year because of deep frustration with economic austerity and anger over the terms being set by the European Union for a financial rescue. Far-right parties have gained ground in France and even in usually moderate Scandinavia.

In the United States, partisan splits have rarely been so deep and acrimony across party lines so intense. But these feelings don’t come from wildly positive views about the parties voters embrace. In a widely discussed paper released this month, Alan Abramowitz and Steven Webster, Emory University political scientists, noted that “one of the most important trends in American politics over the past several decades has been the rise of negative partisanship in the electorate.”