Sarah Palin denies any wrongdoing over the affair
Republican vice-presidential candidate Sarah Palin is "unlikely to co-operate" with an inquiry into alleged abuse of power, a campaign spokesman has said.
Ed O'Callaghan said the Alaska state legislative probe had become "tainted" by partisan Democratic politicians seeking to target the Alaska governor.
Mrs Palin, who is John McCain's running mate, denies any improper behaviour.
A spokeswoman for the Alaska Democratic Party rejected claims that the inquiry had become politically motivated.
The probe into the affair - referred to by some as "Troopergate" - began before Republican presidential nominee John McCain picked Mrs Palin as his running mate last month.
Mrs Palin and her husband campaigned in Colorado and Ohio on Monday. She is expected to make further campaign appearances in Ohio on Tuesday.
'Stall and smear'
Mrs Palin is accused of removing Alaska Public Safety Commissioner Walt Monegan from his post after he had refused her request to fire her ex-brother-in-law, Mike Wooten, as a state trooper.
Mr Wooten was involved in a contentious divorce and child custody battle with her younger sister.
Critics say Mrs Palin was using her power as governor to pursue a personal feud.
The investigation centres on the dismissal of Alaska's public safety chief
Mrs Palin insists that she fired Mr Monegan over disagreements about budget priorities.
A bipartisan panel of the Alaska state legislature voted to authorise an inquiry and in July appointed retired prosecutor Stephen Branchflower to lead it.
Mrs Palin's husband, Todd, has been ordered to testify to the inquiry, as have her chief of staff and deputy chief of staff.
McCain campaign spokesman Mr O'Callaghan said he did not know if Mr Palin would challenge the subpoena, issued on Friday, requiring his cooperation.
However, Mrs Palin was "unlikely to co-operate" with the inquiry "so long as it remains tainted and run by partisan individuals that have a pre-determined conclusion", the AFP news agency quotes him as saying.
Mrs Palin has not been ordered to testify but Mr Branchflower has said he hopes to speak to her about Mr Monegan's dismissal.
Patti Higgins, spokeswoman for the Alaska Democratic Party, accused the Republican presidential campaign of "doing everything it can to stall and smear" the investigation.
Mrs Palin's lawyer has claimed that public statements by the Democratic chairman of the state Senate Judiciary Committee earlier this month indicate that the inquiry is politically motivated.