American politics is now a four-way struggle. Gridlock lies ahead | Daniel DiSalvo and Carlo Invernizzi-Accetti

No one faction is likely to prevail. Instead we can probably expect years of modest and incremental policy agenda

Everyone agrees that American political parties are deeply polarized. However, last week's elections point to a new political dynamic. While there's no doubt that the two main parties remain bitterly hostile to one another, new fault lines within them will take center-stage.

Intra-party factions have a long history in American politics and have often been engines of change. Emerging now is a four-way struggle between ideologically distinct factions, which may render compromise difficult.