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In declaring his intention yesterday to challenge Senator Gary Humphries for the No.1 spot on the ACT Liberals' Senate ticket for the election on September 14, Zed Seselja is setting down a well-worn path in Australian politics.

Many politicians have made the transition from the state or territory arena to Federal Parliament, among them the former NSW premier and serving Foreign Minister, Bob Carr. Senator Humphries is another, having served as the ACT chief minister before losing office at the 2001 election and taking up a casual Senate vacancy caused by the resignation of Liberal senator Margaret Reid in 2003.

However, the journey is not to be attempted lightly, particularly if the aspirant lacks a high public profile, a solid curriculum vitae and the strong support of local branch members or, failing that, the patronage of powerful figures within his or her party.

As the Canberra Liberals' leader who presided over impressive gains for his party at last year's ACT election, Mr Seselja certainly is not lacking in the name-recognition department, but it is not clear that his CV stamps him as an unmistakably better candidate than Senator Humphries, or that he has a patron within the party who is ready and able to grant him a "captain's pick''. Indeed, by backing Senator Humphries, Liberal leader Tony Abbott seems to have ruled out a parachute for Mr Seselja.

Doubtless, Mr Seselja and his backers have been busy courting rank-and-file ACT Liberal Party members. Just how successful any vote-gathering exercise has been will not be known until the actual preselection. ACT Chief Minister Katy Gallagher certainly seems to believe Mr Seselja would not be announcing his candidacy unless he had stitched up the required number of votes, but then it is in her (and Labor's) interest to suggest this is a fait accompli.

Rumours have been circulating in Canberra political circles for some months that Mr Seselja is preparing to move to the House on the Hill. Then, as now, Senator Humphries' response has been that he is not about to stand down, and that he looks forward to ''offering good reasons why I should be preselected once again for the Senate seat''.

On the face of it, Senator Humphries seems to have a stronger case for preselection in the No.1 spot. Aside from his experience as chief minister, he has served on the opposition front bench since 2009, and could be expected to be in the running for a ministerial position in the event that the Coalition wins government in September. With no experience at the federal level, 35-year-old Mr Seselja (he turns 36 next month) could expect no such promotion, meaning the ACT would have no ministerial representation in the federal government.

Having voted, for example, to reverse the Howard government's ban on the ACT's civil unions law, Senator Humphries might also argue that he is more socially liberal in his ideology and outlook than Mr Seselja, an important consideration in a socially progressive electorate like the ACT. The Liberal Party is less tolerant of those with centre-left leanings than it used to be, and though this might aid the future advancement of a politician like Mr Seselja, there is no indication yet that the ACT electorate as a whole is embracing social conservatism.

One distinct advantage Mr Seselja has over Senator Humphries is his youth and the fact that he presents as "a fresh face'', though, at 54, the latter can hardly be characterised as over the hill. Last year's territory election indicated that Mr Seselja has a strong personal following in Tuggeranong, another point in his favour. Many of those voters, however, might be wondering now why they bothered supporting Mr Seselja when he is not sticking around to represent their interests.

The potential for this battle to be divisive - and to deliver no net gain to the party in terms of Senate representation - is something that will concern many Liberal voters. Indeed, some may question why it is that Mr Seselja, with his strong support base in Canberra's south, does not contest the lower house seat of Canberra. Wresting Canberra, held comfortably by Labor's Gai Brodtmann, might be a near impossible assignment, but it would demonstrate Mr Seselja's willingness to "pay his dues'' and pave the way for a future tilt at the Senate.

There is perhaps no more thankless task than leading an opposition party over the long haul, but in his impatience to leave the job only three months after leading the Liberals to their biggest ACT vote since 1995, Mr Seselja may be subjecting his party to needless division and discord.