Speculation is simmering that Abe will call a snap lower house election in tandem with the upper house poll this year.

Japanese Prime Minister Shinzo Abe‘s ruling bloc has suffered two rare losses in by-elections, an apparent warning from voters ahead of a national election for parliament’s upper house later this year.

Sunday’s defeats in a lower house by-election in Osaka, western Japan, and another on the southern island of Okinawa – host to the bulk of US military in the country – were the first such losses since Abe returned to office in December 2012, except for one uncontested poll.

“Each individual [ruling] Liberal Democratic Party member must take the results to heart and buckle down,” Abe told reporters on Monday morning.

The defeats in the polls come after Japan’s Olympics minister, Yoshitaka Sakurada, resigned a year before the Tokyo Olympics. A vice transport minister also quit over a separate gaffe.

“The cabinet support rate is maintaining a certain level, but if they do not eradicate laxity and conceit, the upper house election will perforce be a difficult fight,” said an editorial in the conservative Yomiuri newspaper.

In a survey by public broadcaster NHK released this month, support for Abe’s cabinet was at 47 percent, up five points from the previous month.

In Okinawa, Tomohiro Yara, a freelance journalist backed by several opposition parties and running on an anti-US base platform, defeated a former cabinet minister.

In Osaka, Shimpei Kitagawa, backed by the Liberal Democratic Party or LDP and its junior partner Komeito, lost to Fumitake Fujita from Nippon Ishin.

Speculation is simmering that Abe will call a snap lower house election in tandem with the upper house poll, possibly after announcing the postponement of a sales tax hike to 10 percent from eight percent scheduled for October.

Top government officials vowed on Friday to go ahead with the tax rise, barring a big economic shock.

Such a “double election” might help take advantage of weakness among the fragmented opposition parties, but could also spark the opposition to cooperate on candidates.

“Abe must be wondering which suffers more from weakness – LDP/Komeito or the opposition,” said Sophia University political science professor Koichi Nakano.

“A double election will also potentially galvanise the opposition into action … so it’s a double-edged sword.”