Palin was also lambasted this week for failing to correctly spell out the vice president's role on several occasions, including during the vice presidential debate with her Democratic rival Joseph Biden.
Responding during one television interview to a question sent in by an elementary school pupil about what the vice-president does, Palin again overstated the White House second-in-command's powers.
"They're in charge of the United States Senate, so if they want to they can really get in there with the senators and make a lot of good policy changes," she said.
The comment directly contradicted the separation-of-powers principle enshrined in the US constitution, under which the vice-president as president of the Senate has a casting vote in the event of a tie, but takes no other role.
McCain has staunchly defended his running mate against the slew of attacks, stressing she will be a valuable asset in his campaign goal of ridding Washington of political corruption.
But even staunch Republicans remain unconvinced.
Ken Adelman, a Republican hawk who served in top diplomatic and defense posts for presidents Gerald Ford, Ronald Reagan and George H.W. Bush, told the New Yorker magazine that Palin's choice for vice president made him switch sides and he is now supporting Obama for president.
Former secretary of state Colin Powell, a Republican and military general who has also served as chairman of the joint chiefs of staff, on Sunday endorsed Obama and said of Palin: "I don't believe she is ready to be president of the United States, which is the job of the vice president."
And one of former president George H.W. Bush's speechwriters, Christopher Buckley, a prominent conservative, announced this month he was abandoning support for McCain for many reasons, including "the Palin nomination. What on earth can he have been thinking?"