WASHINGTON (AP) — National Republicans are investing $500,000 in the Pennsylvania Senate race as polls show a closer contest between Democratic Sen. Bob Casey and Tom Smith, a wealthy tea party candidate who has invested more than $16 million into his run.

An official with the National Republican Senatorial Committee said Friday that the organization was giving half a million dollars in initial coordinated funds to Smith. The official spoke on condition of anonymity to freely discuss ad buying and election strategy in the race.

Casey is bidding for a second term. Smith made a fortune in coal mining and has been on course to outspend Casey by 2-to-1 after July 1.

A Quinnipiac University poll released last week showed Casey with 48 percent, versus Smith's 45 percent.