When the results of the election for the mayor of Tokyo's Chiyoda ward were announced on February 5, there was a very brief stunned silence. Masami Ishikawa was the incumbent and retained his seat, but the scale of his victory over the candidate put forward by the ruling Liberal Democratic Party (LDP) was what resonated with all present.

Ishikawa won 16,371 votes, leaving Makoto Yosano a distant second with a mere 4,758 votes.

Ishikawa's campaign was aided immeasurably by his membership of the "Tomin First No Kai" - which translates as the Tokyo residents' first group - set up by Tokyo Governor Yuriko Koike. And while her fledgling political organization is presently focused on doing what is in the best interests of residents of the metropolis, there are hints that she has ambitions on a national scale.

Rivals 'very worried'

And that, say analysts, has Japan's traditional political parties very worried. And none more so than the LDP.

"Sunday's result was a slaughter," said Jun Okumura, a visiting scholar at the Meiji Institute for Global Affairs. "It was so embarrassing that I have heard that the head of the LDP's faction in the metropolitan assembly is not going to run for re-election in this summer's poll because their candidates have been doing so horribly."

Before the latest election, Koike had suggested that she would aim to field between 30 and 40 candidates in the summer election for the metropolitan assembly. Now she is planning to contest 60 of the 127 seats in the assembly.

"I think that Ishikawa's victory means that I have also obtained significant support," she said after the results were announced. "I will make efforts to spread my drastic reform agenda to the whole of Tokyo."

Ironically, Koike is herself a member of the LDP - although she did joke in a recent interview that she has not paid her membership fees since December so she is teetering on the verge of being a former member of the party - but a growing disillusionment with the party and anger at what she saw as chronic mismanagement in the running of Tokyo encouraged her to stand for election as an independent for the governorship.

Previous administration

In August 2016, she replaced Yoichi Masuzoe, who had been caught out spending political funds on "improper" purchases that ranged from expensive art to children's pajamas.

And in the six months since she took office, her hard-working, combative style and desire to do the best for the people of Tokyo have won her further support. Indeed, three LDP members of the chamber have defected to her camp and the Komeito party, which is nominally an LDP ally, has invariably voted in support of her policies.

"The LDP is running scared of Koike because it is very likely that she will be taking seats from the LDP in the summer elections, but they have so far resisted the temptation to expel her from the party because they fear that could give her the excuse she needs to go into national politics," Okumura told DW, adding that they would be far happier if she concentrated on righting wrongs in Tokyo rather than shining the spotlight on mismanagement at the national level.

Two issues have really cemented Koike's popularity among the electorate. The first is her handling of the scandal surrounding the planned relocation of the city's wholesale fish market from Tsukiji to a man-made island in Tokyo Bay. The buildings and infrastructure for the new facility have been built - but an investigation has shown unacceptably high levels of contaminants, including benzene 79 times legal levels, arsenic and cyanide.

Inquiry ordered

The allegation is that developers cut corners, with the tacit approval of city planners. But Governor Koike is having none of it, has delayed the transfer and ordered an inquiry.

Her second campaign has been in connection with Tokyo hosting the 2020 Olympic Games  and the vast amounts of money that have been earmarked for infrastructure and other facilities. Koike has already achieved some cost reductions and has ordered her staff to find more.

"She has done very well in a short space of time and I would be very surprised if she is not at least contemplating ways in which to keep her options open when it comes to a role on the national political stage," said Okumura.

But Stephen Nagy, an associate professor of international relations at Tokyo's International Christian University, says that while Koike has done well at the city level, time may not be on her side.

Transparency and toughness

"She is popular because she has shown herself to be tough, she has demonstrated leadership, she has cut through red tape, she is willing to stand up to vested interests, she has demonstrated transparency in her administration and she has made sure that taxpayers' money is well spent," he told DW.

"And Japanese voters are happy to have a leader who they see as standing up for their rights," he said.

"And while she has demonstrated her credentials already, she is going to want to stick around until at least the city hosts the Olympics, by which time she will be 68 years old," Nagy points out.

"Also, I do not believe there is any political space between the parties at the national level for another party, so it may be that she decides that her legacy is best served at the Tokyo level, where she will be able to establish a precedent for reform and fair and clean politics."