While they may disagree on tax policy, one thing unites politicians from the left to the right: voter-tracking software.

NationBuilder is a company headquartered in California, yet its logo can be found at the bottom of websites belonging to a number of Australian candidates.

Such services help parties manage data about individual voters, and tailor messaging accordingly. Among the political class, it is the standard stuff of an election run.

Yet the rise of these companies brings growing concern about the data practices of local political parties, especially given these platforms often store Australian information overseas.

The major parties are tight-lipped about their digital capabilities. And they can be, thanks to their political exemption from national privacy legislation, according to David Paris, Digital Rights Watch board member and former policy advisor to Scott Ludlam from the Australian Greens.

"Regardless of the information they collect and the information they use, there's no way for people to opt out, there's no way for people to say that the information they have is inaccurate, or they don't want it used," he said.

Collecting data, massaging the message

NationBuilder helps political campaigns store and sort voter details like name, address, phone number and the kinds of issues they respond to.

If someone undertakes a political action, such as donating or volunteering, the software keeps track and helps candidates encourage them to do more over time, according to Daniel Stone, the executive director of political consultancy Principle Co.

That might include sending a donation request that reflects what a voter has typically given and what they're likely capable of giving, explained Mr Stone, who has done work for the Labor Party and progressive causes.

"You wouldn't want to have an e-mail come into your inbox saying, 'Can you chip in $500?' … but you might be much more sympathetic to an ask of $5 or $10," he said.

In Australia, parties have access to the electoral roll, but online campaigning also provides a fresh opportunity to collect data points about each voter.

Blake Wright, the digital director for bipartisan group Unite America in Denver, Colorado, explained how this works when he runs a Facebook ad campaign promoting a petition.

When people sign, Unite America collects details in NationBuilder like email and zip code.

"Then we get to start matching them back to a voter file or data that we previously had," he said. "We can start blasting e-mails towards them or pushing them into other avenues of engagement."

In the US, NationBuilder offers voter data files, with information including names and whether the person has voted.

This service is not available in Australia, but the platform does provide a social matching tool, which automatically links someone's Facebook profile photo or even their Twitter location to their email address if it is held in the party's database.

The tool is automatically switched on in Australia, explained Toni Cowan-Brown, NationBuilder's vice president of strategic partnerships.

It is not switched on by default in Europe, where new data privacy laws have raised the bar of consent.

The secure campaign

After multiple political data scandals — most notoriously, Cambridge Analytica — the protection of Australian voter data is a significant issue, especially given the popularity of overseas software among political operatives.

Mr Stone said some political groups are now motivated to consider their options and move to other platforms. Sometimes for the sake of cost, but also for greater control over where data is stored.

NationBuilder's servers are US-based, although Ms Cowan-Brown said the company is looking at installing them in other regions.

The use of global servers by online services is far from unusual, but data about Australian voters and their views is seen by privacy advocates as particularly more sensitive.

When asked if there are rules regarding where electoral roll data can be stored, an Australian Electoral Commission spokesperson said it had no role in party cybersecurity measures.

A Labor spokesperson said the party uses software that helps it to "communicate effectively" with the Australian community, while a Coalition spokesperson said the Liberal Party "fully complies with the Commonwealth Electoral Act".

NationBuilder's software was used by both sides of the Brexit campaign in 2016. ( AP: Frank Augstein )

NationBuilder is also strictly non-partisan. It was used not only to support the 2016 Donald Trump campaign but for both sides of the Brexit debate.

For Mr Wright, the apolitical stance of NationBuilder is a benefit, but for other groups more directly aligned to conservative or progressive movements, it can be a liability.

Marcella Brassett, the Asylum Seeker Resource Centre's campaigns manager, has some reservations about her organisation's use of NationBuilder given its use by Republican candidates, for example.

"If you're a movement or a campaign, you do want to think about the ethics of what you're using and the people that you give your money to," she said.

Ms Cowan-Brown said NationBuilder does not believe that "as a tech company" it should decide who has access to the tools.

Does it work, anyway?

Amid the fad for data collection and software solutions, there is still debate over whether highly specific targeting of voters by political parties truly works.

Is it a "magical potion", or are people more likely to decide their vote based on the fundamentals: age, location and lived experience?

Mr Stone believed the latter. Nevertheless, when it comes to targeting, he said politicians have always tailored their message to the crowd.

"There's always been a town hall meeting held in Townsville and a town hall meeting held in Melbourne," he said.

"I'm sure Edmund Barton had radically different things to say to those two different groups."

Yet as software becomes more sophisticated and databases grow, Mr Wright warned politicians against being tempted to excessively massage their message.

"That can be a harmful thing if they're just trying to follow [voter data] rather than lead," he said.