Daniel Markey from the US State Department was asked how much of a “sharp shock” having the former cricket player as Prime Minister is for Pakistan.
Mr Markey replied it was significant in a historical sense because it is the first major civilian figure to get into a prominent position in Pakistani politics for decades.
But, the guest expressed scepticism about whether he will be a “breath of fresh air” as some observers are suggesting.
Mr Markey said: “If he doesn’t win an outright majority he is going to have to continue to work with some of the old forces.
“One of the core criticisms of him and his party over the past couple of years is that he has already pulled in a variety of, what you might call, ‘electables’ of some of the old crowd who themselves have been considered to be more corrupt.
“They are old-fashioned in their practice of Pakistani politics, which raises questions about whether he is really a breath of fresh air in any considerable way and whether he will tackle problems of corruption.”
The US commentator was also asked about Mr Khan’s political views, such as his support of the blasphemy laws, and whether he really believed in the rules or if it was just political “pragmatism”.
Pakistan’s Penal Code prohibits blasphemy against any recognised religion, providing penalties ranging from a fine to death.
Mr Markey replied it was hard to have a clear understanding of his views, but if you take the former cricket star at his word, then he has had a spiritual transformation over the years.
But the official added it could have been to get votes.
He continued: “Either way, he is quite different from Nawaz Sharif.”
Imran Khan of the PTI party is expected to be the biggest party in the election, with an estimated 109 of the 272 contested seats.
To form a government without a deal with one of the other parties, they will need to claim a total of 137 seats.
PMLN, the party of ousted former prime minister Nawaz Sharif, is in second place with 67 seats, and Pakistan’s People’s Party is predicted to take 39.
Many of Mr Khan’s supporters are already on the streets of Pakistan’s town and cities celebrating his victory as if it is a certainty.
The Secretary of the Election Commission of Pakistan, Barbar Yaqoob, has tried to calm rumours of conspiracy and fixing of the election results.
He told reporters on Wednesday night election results were coming in later than expected because of issues with the “transmission system”.
Mr Yaqoob said: “There is no conspiracy, nor any pressure in delay of the results.
“The delay is being caused because the result transmission system has collapsed.”