Lancaster, New Hampshire (CNN) - As his campaign bus wound along the twisting roads of New Hampshire's north country Thursday, Mitt Romney told reporters he would not be adding a one-on-one debate to his schedule anytime soon.
Romney declined a challenge by Newt Gingrich to debate mano-a-mano, saying it would be disrespectful to leave the other GOP candidates out of a Republican forum.
"Until it's narrowed down and other people are no longer part of the process, and hopefully if I'm still part of the process, I'm going to keep respecting others and keep debating on the schedule that we have," Romney told members of the media at a farm and hardware store in Lancaster.
However, Romney said he did expect the field to winnow as voters began to head to the polls.
"It'll probably narrow down at some point to two, maybe three people, as it did last time," Romney said. "It may well be Speaker Gingrich and myself and we'll get that chance."
Gingrich laid down the challenge at a campaign event Wednesday, after Romney charged the former House speaker should not complain about negative ads run against him.
On a long day filled with mostly retail politicking, Romney stopped to address members of the press who are tracking his progress through the state by bus.
The former chief of a venture capital firm said he did not plan to release his tax returns, saying he had released the "pretty extensive" information that was required by law.
"We don't have any current plans to release tax returns, but never say never," Romney said. "We'll see what the future holds."
The campaign has estimated Romney's personal wealth at between $190 and $250 million.
Elsewhere on his bus tour, Romney crossed off items on his Christmas shopping list and pumped gas into his campaign bus on a trek into New Hampshire's north country.
In Littleton, the candidate bought a white puffer coat for his wife Ann at an outdoor clothing store.
Many miles down the road, Romney filled up his campaign coach's gas tank at Lowe's Store in Randolph. In the mini-market, the candidate jokingly offered to buy an antique car from the owners.
The shopkeeper suggested Romney might offer $10,000 - a light-hearted reference to a bet the former governor had offered Rick Perry.
"That's way too expensive for my taste," Romney laughed.
The Romney campaign announced it was releasing an ad in New Hampshire in which the candidate said fiscal discipline is a "moral responsibility."
The ad previously ran in Iowa.