Stephanie Mencimer for MoJo:

This face-off could well be nastier and more expensive than past confrontations over the Supreme Court. It’s the first political fight of this kind since the controversial Citizens United decision allowed money to flow freely into the political system. The influx of money has also helped create a well-funded extra-party political infrastructure that is now turning its sights on the SCOTUS fight.

Thanks to Citizens United, campaign finance rules that once limited the use of corporate and union money for certain advertisements no longer exist. Meanwhile, dark-money groups—which can get involved in campaigns but don’t have to disclose their donors—are supposed to spend slightly more than half of their money on nonelection activities to keep their nonprofit status. As a result, they “may funnel a lot of the rest of their money into Supreme Court-related ads,” says Rick Hasen, an election law professor at the University of California-Irvine law school