A former sporting superstar, passionate conservationist and equality advocate, the Zimbabwean-born Pocock has long been considered the perfect political candidate for a city which leans to the left and loves its rugby.

Aside from Nick Kyrgios, and perhaps Ricky Stuart, is there a bigger name in Canberra - sporting or otherwise?

On this basis, Pocock should surely stroll into the Federal Parliament with the same ease with which he crashed through opponents during an illustrious professional rugby career. Right?

Don't be so sure.

Pocock will campaign as an alternative to both Labor's Katy Gallagher and Liberal Zed Seselja. But with Gallagher all but guaranteed a spot, it's Seselja's seat he's gunning for.

By attempting to topple the Morrison government minister, and thus end the major parties' duopoly over the ACT's senate spots, the 33-year-old is facing a test arguably tougher than anything he confronted on the field.

Seselja has stared down and survived every challenge he's faced since 2013 - including the cashed up, union-backed "Dump Zed" campaign at the last federal election.

There are many and varied theories on how a polarising conservative figure has managed to survive in progressive Canberra.

But one thing cannot be disputed: the numbers are in his - and Labor's - favour.

The basic arithmetic behind the ACT senate race means the Liberals will need just a third of the vote to return Seselja to the upper house.

The Seselja-led Liberal ticket has fallen short of that mark - known as a "quota" - at recent elections, but nevertheless comfortably retained its seat.

Federal and local elections have shown that at least 30 per cent of Canberrans vote Liberal. Seselja might not be everyone's cup of tea, but nor does he need to be.

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So, what hope does Pocock have of pilfering Seselja's seat?

Pocock's simplest path to the Senate would be through winning a quota in his own right, which would be a remarkable feat given he's coming from a standing start and isn't backed by the campaign infrastructure of a major party.

It would be an unprecedented achievement for an independent in an ACT senate race. But has an ACT senate race ever included a candidate quite like Pocock?

The other scenario is far messier, and recognises the reality that this is far from a two-horse race.

Before Pocock's announcements, the biggest threats to Seselja's seat were expected to come from constitutional lawyer Kim Rubenstein and the Greens' Tjanara Goreng Goreng.

The popular view among observers was that Seselja could be in danger if Rubenstein peeled off enough progressive Liberal voters to plunge the party's primary vote into the mid-to-low 20s.

If that happened, the Greens - which polled almost 18 per cent last time around - could be catapulted into the second spot.

The emergence of Pocock complicates the scenario. Could he, rather than Goreng Goreng, benefit from Rubenstein? Could Rubenstein trump them all?

Pocock also threatens to fracture the progressive vote, leaving none of the challengers within striking distance of Seselja.

Whatever happens, Pocock has turned the ACT senate contest into a must-watch race at the next federal election.

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