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Crossroads dropping $10.5M into Senate races in final campaign week

But most of the groups' biggest investments are to shore up struggling Republican candidates in top-tier races. The group is spending $2.3 million in Wisconsin to help former Gov. Tommy Thompson (R), a huge sum in the relatively inexpensive state. They're also spending $1.5 million to help Indiana state Treasurer Richard Mourdock (R), whose recent missteps have put his campaign in a bind.

The other targets are in Montana, where they'll blitz the inexpensive airwaves with nearly $1 million, as well as Nevada, North Dakota, Virginia and Ohio, all Democrat-held seats where the groups have spent months advertising.