The campaign has dispatched him since January on more than a dozen trips to swing states everywhere from Iowa to Florida, but particularly focusing on Utah neighbors Nevada and Colorado.
He's also a constant figure on cable news shows ripping Obama and defending Romney. During a CNN interview in July, he rejected calls for Romney to release more tax records, saying Democrats were obsessed with his wealth.
"Governor Romney's been very successful. Get over it," Chaffetz said.
The Romney campaign is most likely relying on the Alpine Republican because he's telegenic and popular among tea party Republicans, said Quin Monson, a political scientist at Brigham Young University.
"He's out making sure the folks that are sympathetic to the tea party are on Romney's side," Monson said. "He's a talented public speaker. To the right audience, he comes off quite well."
Chaffetz is also unafraid of confrontation. Similar to the role he played in Colorado this week, Chaffetz trailed Romney's opponents in the primaries and famously got in a verbal altercation with Newt Gingrich spokesman R.C. Hammond in January. The media coordinator kept pressing the congressman on his voting record and his support for Romney as TV cameras and a crowd gathered around them. Chaffetz uncomfortably shrugged him off.
There's even talk that Chaffetz could represent the Republican viewpoint at the Democratic National Convention in Charlotte, N.C.
That's quite a bit of time for a man who is running for re-election, but Chaffetz represents one of the nation's most conservative districts.
"For somebody like Chaffetz, he doesn't have to worry about getting re-elected in his district," Monson said. "It's not as if working for Romney will make him less popular."
Romney is beloved in Utah, where he received 93 percent of the state's GOP primary vote.
He also has a large cadre of surrogates, many of whom he has at least considered making his running mate, such as Sen. Marco Rubio, R-Fla., and Rep. Paul Ryan, R-Wis. No one has put Chaffetz on that list, but Monson wonders if he might be angling for another job in a Romney White House.
"This is how campaigns always work. When Obama came to office, he hired people from his campaign. What's Romney going to do when he comes to the White House? Hire people from his campaign team," Monson said.
Chaffetz said he's happy serving as a member of Congress and that his biggest motivator is to oust Obama and "to call Romney Mr. President." He would not, however, rule out an administrative position if called upon.
"You can't turn down something that hasn't been offered," Chaffetz said in a phone call during his visit to Colorado.
Being a regular part of the team, Chaffetz and Romney have formed a friendly rapport. At a June rally in Las Vegas, Romney introduced some dignitaries, but seemed to draw a blank when he came to Chaffetz.
"I gotta skip the guy in the center here, because I'm not sure who that is," Romney joked.
He then mentioned Chaffetz's name, saying: "How he got on the stage, I don't know. But he's a good friend, and he's been traveling with me, and I appreciate his being here."