(CNN) - A veteran Republican strategist who helped engineer John McCain's South Carolina presidential primary victory in 2008 has joined Nikki Haley's gubernatorial campaign as a senior adviser.
Trey Walker, who also advised McCain's unsuccessful 2000 bid, has signed on with the Republican to assist with communications efforts.
Walker is also a longtime aide to Attorney General Henry McMaster and worked for him during the state's contentious GOP primary fight earlier this year. McMaster went on to endorse Haley and became one of her top supporters.
"Nikki Haley's election as governor will be a transformative moment for South Carolina and the cause of conservative, accountable government," Walker told CNN. "I'm honored to play a role in the home stretch."
Haley's opponent in the South Carolina race is Democratic state Sen. Vincent Sheehen.
The staffing move comes as people close to both campaigns acknowledge to CNN that the race has tightened in recent weeks, perhaps approaching a single-digit margin.
The trend is due in part to Sheehen's television ads, which have raised the profile of the relatively little known lawmaker while also raising questions about Haley's self-styled reputation as a reformer.