Xenophon describes himself as an accidental politician. A personal injury lawyer, he was drawn into politics by "cumulative rage against the machine" as he observed the social harm caused by poker machines.

"Client after client [was] telling me about their problems or family problems." A brain-injured client wept at losing nearly $30,000, his entire emergency superannuation payout. He had been treated like a king by the venues that exploited him - free booze, free meals, travel to and from, friendship - until the money ran out, "and the worst thing was, this guy couldn't understand why".

Xenophon ran on the anti-pokies ticket in 1997 and was elected to the State Parliament with less than 3 per cent of the vote.

Xenophon admits to three days in Las Vegas 20 years ago when he "lost 30 big ones" playing the pokies. A "big one" was an American dollar. He joked that he stopped buying lotto tickets after his election because, if he won $15 million, he would have to make a video - a la Pauline Hanson - declaring: "If you see this video, it means I have gone to the Bahamas."

But gambling, he says, is no laughing matter, although he would like to partake in a Melbourne Cup sweep. "But people avoid me during sweeps … they're worried I'll jinx it," says Xenophon, who is of Greek Cypriot heritage and Greek Orthodox faith.

Apart from a sip to toast a wedding, he is teetotal, and says a heart condition keeps him off coffee. He enjoys herbal tea and is known to carry his own tea bag in a pocket, just in case.

Xenophon insists his health is fine now, but in 2002 he had open-heart surgery and he suffers from recurrent back pain.

"I'll have to find a decent physio in Canberra if it seizes up on me. I'm sure there will be lots of people wanting to manipulate me in Canberra."

He shuns the perks of office. He flies economy class and prefers to hire cars or use taxis rather than use the Parliament's limousine fleet. "I'd rather be in the driver's seat."

It may take time to get used to his Parliament House suite. "My office in State Parliament was under a stairwell, Harry Potter-like almost, which I was quite happy with."

People who donated to his election campaign got money back when he received his public funding. "I ended up giving back 88 per cent of the money."

It is not easy to pigeonhole Xenophon as being left or right. He does not support voluntary euthanasia but backs the South Australian approach of not treating as an offence the administration of painkillers that might, as an unintended consequence, hasten death. "I think that is the right balance."

He does not want to see changes to abortion laws but believes spending more on education could reduce the abortion rate. "I don't think anyone thinks it's desirable that 14- and 15- and 16-year-old girls get pregnant, so I think you can do that without restricting a woman's right to choose."

He accepts stem cell research as long as there are strong ethical safeguards. He opposes genetically modified food.

He is cautious on gay marriage but says he would "seriously consider allowing" the ACT civil union legislation.

He would like taxpayers asked on their tax returns whether they want to donate all or some of their refunds to charity.

Xenophon was always something of an individual, if not an eccentric, and fascinated by politics.

He attended Adelaide's elite Prince Alfred College, where his ethnic heritage put him in a minority; he went on to study law at Adelaide University, where he immediately signed up to the campus Liberal Club. He admits to also "dabbling" with Labor and the Democrats.

In the late 1970s, when the hard left dominated Adelaide student politics, the teenage Xenophon was elected editor of the university student newspaper, On Dit , with the support of the campus Liberals. But Xenophon was to fall out bitterly with his Liberal friends.

He took the job of student editor seriously, running exposes of bastardry at a university college favoured by the Adelaide establishment, and refused to treat the newspaper as a propaganda sheet for his political allies.

When he discovered that some student Liberals had rorted a campus election, he quit the Liberal Club and exposed the affair in dramatic circumstances. "My election as editor was actually rigged with false ballots and I didn't know the extent of that until halfway through my term. It was pretty ugly at the time," he says.

While finishing his law studies, Xenophon displayed an entrepreneurial streak, running a revival movie house in suburban Adelaide. He tried unsuccessfully to get finance for a documentary film on Australian wrestlers, spending a lot of time tracking down and interviewing old stagers such as Mario Milano.

"In some ways, professional wrestling is a bit like politics. There's a lot of theatre going on, a lot of grunting and groaning without either much reason or much effort."

The audience is now keen to see how Xenophon wrestles with the Government and the other balance-of-power senators.

His South Australian reputation was one of indecisiveness. Now, he says: "Where the Liberal Party is voting differently from Labor, those bills will require a very close forensic examination. It's not unreasonable for people to know what my stand is on each bill, but at this stage I think I'll have five staff members and we're going to be bloody busy."

He admires the way the Tasmanian independent Brian Harradine extracted largesse for his state by wielding his critical Senate vote. "I need to advocate for my state, and look after the state's interests."

He names Tim Costello as his mentor. The director of World Vision Australia campaigned for him as an anti-pokies candidate, and "we've kept in constant contact".

He has not met the Prime Minister, but is looking forward to it.

Xenophon has struck up a friendship with the Nationals senator Barnaby Joyce (who could, on occasion, be an "eighth option" open to the Government to win a vote). "We're in very regular contact. We speak at least once or twice a week. He's quite passionate about a number of issues, including trade practices reform, and we get on terrifically well. Doesn't mean we're going to agree on everything; we won't."

There has been contact with the Greens leader, Bob Brown, over the years. Xenophon describes it as cordial. "We don't necessarily see eye-to-eye but you have to respect the man for his persistence, his passion, and he has played a very important role in Australian politics."

There seems to be less of a relationship with Steve Fielding of Family First. "I sought him out and I met him in Melbourne a few weeks ago, and I want to have a cordial relationship with him," says Xenophon, who recalls how he was approached seven or eight years ago by a number of Assemblies of God ministers.

"They wanted to join up with me. I said I don't want to be part of a party." He suggested they set up their own party. They asked for naming advice. "I said you can always call it Family First."

Xenophon says water and the Murray River have become his priorities. He will not physically sit on the Senate crossbench until the upper house resumes on August 26. Until then, a lot could change.

Asked about his switch from endorsement to denunciation of the Government's FuelWatch program, he quotes John Maynard Keynes: "When the facts change, I change my mind." It's time, he says, to take a good look at wholesale competition and import parity pricing of indigenous crude oil.

Xenophon's ability to prevaricate has driven others mad.

Michael Armitage last encountered Xenophon when Armitage was the minister in the South Australian Liberal government partly responsible for selling the state's electricity assets.

The sale was every bit as controversial as the power issue is in NSW today. Xenophon held the deciding vote. He dithered for almost a year before allowing a less than perfect lease deal.

Ten years on, Armitage, now chief lobbyist for the private health funds, once again must negotiate with Xenophon, needing his vote to block Labor's plans to double the punitive Medicare levy surcharge threshold.

He has only kind words to say about the man who once frustrated him so.

"Nick is a very effective politician, he's very good at getting coalitions of interest, and he's intelligent," Armitage said this week.

Greg Kelton, the veteran state political editor for Adelaide's The Advertiser says Xenophon's success is due to his having changed from being a single-issue politician to "people's champion".

"He is a media tart, but his heart's in the right place." The Senate transition, Kelton says, will be mostly smooth for a man who "doesn't give his vote lightly" and who is "a good horse-trader".

Xenophon helped unite South Australia in outrage when the prominent lawyer Eugene McGee got off lightly for a hit-run accident in 2003 in which he struck a cyclist and left him to die. Xenophon became an advocate for the victim's wife, and public opinion eventually forced a royal commission that led to harsher laws for hit-run offences.

But the state's Rann Government is not sad to see his back. "He's a snake; he does a deal with the last person he spoke to," said one person who dealt with him over years. "He's a game player; he never knows which position he wants. He sniffs the wind and goes with the most popular position."

Safe in the knowledge that he never has to deliver for the underdogs, he sides with them.

Said another: "Everyone likes him. He's amiable, he's puppy-dog-like, he needs attention. But he's hard to trust; he just doesn't keep his word. He can't stick to a deal, he can't keep a promise. It's always about him. He's burnt nearly everybody here."

One story goes that he persuaded the Premier to fund a a solicitor for the hit-run victim's widow, on the promise he would not use it for self-promotion. Half an hour after Rann rang Xenophon to inform him of approval, the evening news carried a report detailing Xenophon's success in negotiating the free legal representation.

These days, Rann is diplomatic - just.

He said Xenophon needed to lift his game above stunts to "demonstrate he can be serious" in "a serious job".

And Xenophon's opinion? "I don't think I endeared myself to the Premier when I dressed up a dog as the Premier."