Outside groups are spending another $1.5 million in Indiana's deadlocked Senate race this week.
A collaboration of Democratic-aligned groups announced plans Tuesday to spend $1 million on an ad attacking Republican Richard Mourdock for opposing the Chrysler bankruptcy in 2009.
The anti-tax Club for Growth, meanwhile, said it would spend $500,000 in Indiana.
This week has become the most expensive of any Indiana Senate battle as groups bought a $2.75 million of air time.
Mourdock spent $300,000 Monday on a new ad attacking Democrat Joe Donnelly for being "too liberal," and Senate Democrats spent another $439,000.
A Republican tracking ad buys confirmed Tuesday that the National Republican Senatorial Committee was spending $500,000 this week. The Republican requested anonymity because the NRSC does not openly talk about numbers.
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