The senior party strategist Karl Rove has suggested that the former Republican vice-presidential candidate and Alaskan governor Sarah Palin lacks the "gravitas" needed to win the American people's votes, reports the Telegraph.

In an interview, Rove stresses the importance of candidates giving voters the confidence that "they are up to the most demanding job in the world" and argues that Palin needs to prove she is up to the job.

In relation to Palin's upcoming Discovery Channel reality-TV show, in which she is to explore the Alaskan wilderness, Rove says he is "not certain how that fits in the American calculus of 'that helps me see you in the Oval Office' ". He points out that the programme's promotional material, which features Palin saying she "would rather be doing this than in some stuffy old political office", could be particularly problematic for any presidential campaign.

Rove, who was deputy chief of staff under George W Bush, also implies that Palin may struggle in the presidential primaries, which begin in the new year, noting: "It's going to be blood, it's going to be sweat and tears and it's going to be hard effort."

Palin is a divisive figure for Americans, and Rove suggests that, despite strong grass-roots support for her, the race for the Republican primaries is wide open. "Outside of the true believers", he says, most Republican primary voters are still undecided and open to persuasion.

Early indications are that Palin does indeed intend to run for the presidency. She has recently given a speech in Iowa, site of the first caucuses, and is reported to have been gathering both money and staff.

As the race for the Republican presidential nomination tightens, more heavyweights will weigh in on the contest, with potential dividing lines emerging between established figures such as Rove and newer, more divisive candidates with substantial popular support.