Terry Nelson, political director of the Bush-Cheney campaign in 2004, will be senior adviser to Straight Talk America, according to several officials familiar with the hiring. They spoke on condition of anonymity so as not to pre-empt an announcement by McCain's committee.
McCain is using the PAC to raise money and organize his travel on behalf of Republicans running in November's midterm elections.
The PAC is also a launching pad for what most Republicans consider to be a likely presidential race by McCain. Nelson's hiring puts him in position to play a major role should McCain seek the White House again.
The Arizona senator ran in 2000, upsetting Bush in New Hampshire but losing the nomination in a bitter two-way race. The Bush and McCain camps eventually came to terms and McCain campaigned vigorously on Bush's behalf in the 2004 re-election campaign.
McCain is courting Bush's supporters, major fundraisers and advisers. Mark McKinnon, the president's chief media strategist, has signaled his willingness to help McCain unless Secretary of State Condoleezza Rice or Florida Gov. Jeb Bush gets in the race.
Both Rice and the president's brother have said they will not run.
While some of Bush's former aides may line behind McCain's potential GOP presidential rivals, Nelson's hiring may help McCain cast himself as the early front-runner and potential heir of Bush's political machine.
Nelson, a soft-spoken Iowa native, is well-respected Republican consultant who served as deputy chief of staff and director of political operations at the Republican National Committee from January 2002 until he joined Bush's re-election campaign.
In 2004, Nelson helped put together Bush's well-oiled grass roots operations. Nelson was political director for the House Republican campaign committee during the 2000 election cycle.