Democrats are leaving nothing to chance in the final leg of the midterm election campaign, outspending Republicans by a wide margin in the parties' battle for control of the House.

With less than a week left before Election Day, campaign cash is flooding into battleground congressional districts around the country as Democrats seek to win back control of the House.

In just the last week alone, political action committees have shelled out more than $340 million in so-called soft-money spending, mostly on campaign ads favoring one party over another. These outside spending groups aren't limited in how much they can spend, as long as they don't coordinate directly with a candidate.

The bulk of that cash — more than $200 million — is being spent in the 30 districts rated as "toss-up" by the Cook Political Report.