Campaign telephone calls are rapidly peppering the US ahead of the country's election and Trump's are outpacing Clinton's in vast numbers.

"In the last 30 days, legitimate campaign calls for Trump have outpaced Clinton by 388%," according to a spokesperson for Hiya, a caller ID and spam blocker, that surveyed 2,007 its mobile phone users in an online poll.

These calls are actually being made by real people, not computers, as the US Telephone Consumer Protection Act bars political robocalls to mobile phones. The high cost of using operators means Trump-associated groups are pouring money into these campaigns.

Campaign calls from Trump and Clinton camps have kicked into high gear since July, increasing 20% between then and September.

But customers are most likely to be turned off by these campaign tactics the survey found. About three out of four people who responded to the survey said they wouldn't answer the call if they knew it was looking for a donation or campaigning for either Clinton or Trump.

Scams that masquerade as political campaign calls have also have also swelled around the election the survey conducted Harris Poll discovered. Since the beginning of the year these calls have grown by 614%.

Among them are voter verification, campaign donation, and election survey scams. These seek personal information and even credit card details to defraud their victims.

Scams aside, legitimate campaign calls appear to be targeting key battleground states. "[The] swing states Florida and Pennsylvania are where a majority of Clinton's calls originate," said a Hiya release.

"With less than one month until Election Day," it said, "call behaviour could be indicative of the state of the election."