Conservative groups outspending liberal counterparts 4 to 1 on congressional races

The Washington Post reports:

Conservative interest groups have dumped well over $20 million into congressional races so far this year, outspending their liberal opponents 4 to 1 and setting off a growing panic among Democrats struggling to regain the House and hold on to their slim majority in the Senate.

The surge suggests that big-spending super PACs and nonprofit groups, which have become dominant players in the presidential race, will also play a pivotal role in House and Senate contests that will determine the balance of power in Washington in 2013.