In a video with 'THANK YOU' written in yellow lettering, the man who will be Ireland's youngest Taoiseach told his 95,000 followers of his rise from an "opinionated, moody teenager" bristling at lack of educational help for his autistic brother.
Harris, sometimes dubbed the "TikTok Taoiseach", is among a vanguard of European politicians embracing the Chinese-owned social media platform, calculating that the need to reach younger voters outweighs security concerns.
With European elections approaching in June, mainstream politicians are wary of ceding ground to fringe parties who have successfully exploited its short video format.
But TikTok is under increasing scrutiny in the West due to fears that user data from the app owned by Beijing-based company ByteDance could end up in the hands of the Chinese government.
Germany's security agencies, for example, have warned against using the app over concerns it could share data with China's government or be used to influence users.
In the U.S., lawmakers want to force a sale of the platform by its Chinese owner or ban it from app stores. President Joe Biden has raised concerns with Chinese President Xi Jinping.
MACRON AMASSES 4 MILLION FOLLOWERS
TikTok says security warnings are unwarranted and it does not collect more information than other apps.
In a bid to assuage concerns, it launched a site to store European users' data in Dublin last year and hired a third-party security firm to monitor data flows.
ByteDance has denied using its product for spying, while the Chinese government has also denied any such intention.
Harris, 37, was an early adopter in March 2021, producing videos that ranged from a 60-second budget summary with musical background to footage of him making a cup of tea when watching football.
Another was French President Emmanuel Macron, who boasts 4 million followers since joining TikTok in 2020.
In Germany, the embrace of TikTok by senior politicians is a newer trend, with Health Minister Karl Lauterbach becoming the country's first minister to open an account in March.
"Revolution at TikTok: it starts today," he said.
"We cannot leave social media to the AfD", he said, of the far-right Alternative for Germany (AfD) party that surged to become Germany's second-most popular.
He was joined on Monday by his boss, German Chancellor Olaf Scholz, who launched his own TikTok account and said on X: "I won't dance. Promise."
The caption for his first TikTok video, set to quirky music, read: "We are just as surprised as you are! (And yes, the Chancellor really is on TikTok now)".
Germany's top ministers have long had an established presence on other social media. For example, Scholz, the finance minister, the economy minister and the foreign minister all have Instagram accounts, as does Lauterbach.
Reaching young voters is particularly pressing as 16-year-olds in Germany can vote in the June European elections.
MAINSTREAM PARTIES 'PANICKING'
Among German parties, the AfD dominates TikTok. The party has 411,000 followers, its top candidate Maximilian Krah 41,000.
"So all the other democratic parties are kind of panicking at the moment not to leave this important platform and the young demographic, the young voters, to this radical party," said political consultant Johannes Hillje.
In one video, Krah encourages school pupils to confront left-wing teachers. Another sees him dispensing dating advice to young men, telling them to not watch porn or vote for the Greens. "Real men are right-wing, real men have ideals, real men are patriots."
Mainstream politicians wanting to emulate such reach face a dilemma because they are also suspicious of using a platform from an authoritarian country.
Lauterbach said he can have reservations about TikTok while recognising its effectiveness. "I don't give the platform any legitimacy by using it," he said. To prevent data leaks, he bought a separate phone for TikTok use.
Macron's team also says the French president sees TikTok's usefulness and the need for regulation as separate issues. "We cannot ignore this population, the vast majority of whom do not watch television news or read the press," an adviser who did not wish to be named told Reuters.
Showing the level of security concern, Britain and Austria banned TikTok from government employees' work phones last year.
But TikTok is becoming harder to ignore. A report by the Reuters Institute for the Study of Journalism last year found that fewer people were putting their trust in traditional media with more turning to TikTok for news.
TikTok was the fastest growing social network in the report, used by 20% of 18- to 24-year-olds for news.
In the UK, the most senior minister with a significant presence on TikTok is Defence Secretary Grant Shapps.
When the TikTok ban on government devices was announced, Shapps responded on the platform with a clip from the 2013 film "Wolf of Wall Street", where Leonardo DiCaprio's character Jordan Belfort declares: "I'm not ******* leaving".
Shapps added that he had never used TikTok on government devices, and that the ban was sensible.
Belgium banned ministers and civil servants from installing TikTok on their official devices but politicians get around this by using the app on separate devices.
The co-ruling Green party's politicians post TikTok videos with devices that are only connected to 4G and have no other apps installed, and the phones are not kept by the politicians themselves but by their employees.
"Another reason we are on it (TikTok), is that we don't want to leave the field to the far-left or the far-right," a Green party spokesperson told Reuters.
"Young people get news through social media and TikTok is one of the biggest platforms. Some politicians are comfortable with that, others are not."
