U.S. Ambassador to China Jon Huntsman Jr. is expected to run for president when he returns to the United States next month.

Roberts is the president of Smart Media Group, the single largest political media buying operation in the country during the 2010 cycle — doing work for Sens. Marco Rubio (Fla.) and Jerry Moran (Kans.) as well as for the gubernatorial campaign of former eBay CEO Meg Whitman in California.

Media buying is one of the least understood but most critical pieces of any large-scale campaign; knowing where (and when) to place ads as well as maintaining relationships with local station managers to help get ads placed (or pulled) matters — particularly in the hurly burly of heated campaign. (And, yes, we just used the words “hurly burly”.)

The hiring of Roberts comes just days after a group of Horizon PAC strategists gathered in New Orleans to talk about the possibility of a 2012 presidential bid by Huntsman. Huntsman was not in attendance although operatives with ties to Michigan, Florida, New Hampshire and South Carolina were, according a source familiar with the gathering.

Huntsman is slated to formally resign his position and return to the U.S. next month, at which time he will consider running for president in 2012. While officials at Horizon PAC are not in communication with Huntsman, the level of hires the organization has made in recent months suggest that the former Utah governor is nearly certain to run.

John Weaver, a longtime political adviser to Sen. John McCain, and media consultant Fred Davis are leading the Horizon PAC effort.

In addition to Roberts, the PAC has brought on a fleet of communications staff including Tim Miller, formerly of the Glover Park Group and McCain presidential veterans Matt David, who also served as California Gov. Arnold Schwarzenegger’s deputy chief of staff, and Jake Suski. The PAC has also signed on early states operatives like Peter Spaulding (New Hampshire) and Richard Quinn (South Carolina). (For a full look at Huntsman’s political inner circle, check out our piece laying it out.)