American Crossroads and its sister group, Crossroads GPS, are launching a $10 million campaign to boost Republicans in four key Senate races.

Crossroads GPS, the nonprofit part of the organization, will spend $3.6 million in North Carolina, $2.3 million in Colorado and $900,000 apiece in Alaska and Arkansas. Those totals will be matched by American Crossroads in Alaska and Arkansas.

The ads will start soon and run on and off through the end of the summer.

American Crossroads has already spent heavily in North Carolina to boost Thom Tillis (R) in his primary, which he won, and has been on the air in Alaska to boost candidate Dan Sullivan (R).