The Republican-affiliated sister groups American Crossroads and Crossroads GPS will begin a massive $10.5 million Senate ad blitz today and Wednesday, blanketing competitive Senate races from Maine to Montana to New Mexico with hard-hitting attack ads.

With control of the Senate in the balance, the deep-pocketed groups are making a concerted final push to help put GOP candidates over the line.

The ads that begin today are in the following Senate races: …