He tells The Associated Press that he'll make a formal announcement Monday.
The seat is held by Republican Sen. Jim DeMint. DeMint has become a top target for Democrats after he said the GOP could make the health care issue President Barack Obama's Waterloo.
The 38-year-old McGowan of Rock Hill said today that for now he's not going to talk about DeMint's conservative views.
He says he'll spend the next few months putting together an organization for the 2010 race. DeMint has close to $3 million for his second term re-election bid. McGowan says he only expects to come up with two-thirds of that.
DeMint unopposed in GOP primary. Meanwhile, Mike Ruckes of Summerville is running on the Democratic side