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, including those in Maine, Montana and 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:

•Montana, backed by $965,000:

•Wisconsin, backed by $2.3 million:

•Maine, backed by $333,000:

•Two in Virginia, backed by a combined $2.2 million:

•North Dakota, backed by $391,000:

•Nevada, backed by $461,000:

•Ohio, backed by $1.5 million:

Ads in Nebraska, New Mexico and Indiana begin Wednesday, backed by $420,000, $512,000 and $1.5 million, respectively.