A group spearheaded by Lehigh County Republican Party chairman Wayne Woodman and the Washington, D.C.-based National Republican Senatorial Committee are spending more than $800,000 combined to help Smith.
Smith's campaign is already on pace to outspend Casey's campaign by two-to-one after July 1.
Casey's endorsed by the state's major newspapers in his quest for a second, six-year term. Smith is a political newcomer who made a fortune in coal mining.
Smith's campaign says the NRSC is contributing $500,000. The biggest contributor to Woodman's group, "Fight for the Dream," is Rosebud Mining Co., which bought Smith's mines in 2010. It gave $240,000.