Speculation that Prime Minister Shinzo Abe will call a double election this summer is evaporating due to fears that dissolving the Lower House for a simultaneous snap election might prove to be a risky gambit.

Some ruling Liberal Democratic Party insiders had suggested that a double election would generate greater energy and momentum among local party organizations and lead to higher vote numbers of party candidates.

However, private surveys conducted by the LDP indicate strong support for party candidates and, according to several government sources, that convinced Abe the LDP would do well even if only the Upper House election was held.

One reason for not holding a double election is to avoid the risk of losing the current two-thirds majority in the Lower House held by the LDP and junior coalition partner Komeito. A two-thirds majority is needed in both chambers of the Diet to initiate a constitutional amendment, which remains high on Abe's political agenda.

Abe will leave on June 12 for a three-day trip to Iran, where he is expected to meet with President Hassan Rouhani and Ayatollah Ali Khamenei, Iran's supreme leader.

A final decision on how to proceed will likely be made before the end of the current Diet session on June 26. As it now stands, the Upper House election is expected to be held on July 21.

One reason for concern among LDP lawmakers about the Upper House election is the huge victory enjoyed by the party in 2013 when the seats that will be up for a vote this time were decided. The LDP won 65 seats six years ago and there was some concern that a counter-reaction to that victory would lead to fewer number of seats won this time around.

A total of 124 seats will be contested in the Upper House election.

While there was some talk about holding a double election, the LDP scored impressive results in the unified local elections held in April. Approval ratings for the Abe Cabinet, meantime, have remained stable.

Moreover, the private surveys by the LDP have shown LDP candidates ahead in many of the prefectural districts.

"There is no longer the feeling that a double election is absolutely necessary," said a high-ranking government official.

Another factor is that there are no pressing issues that provide the rationale for dissolving the Lower House and asking voters to cast ballots on a major initiative.

For example, negotiations with Russia to resolve the dispute over the Northern Territories have made next-to-no progress.

Abe was also asked June 10 whether he was contemplating delaying an increase in the consumption tax rate for a third time. The increase, from the current 8 percent to 10 percent, is scheduled for October.

He explained that although the manufacturing sector is still not robust, another delay in raising the tax rate is out of the question. Abe also noted that there is no major economic crisis, such as in 2008 when U.S. investment bank Lehman Brothers collapsed, triggering a global downturn.

Another extension could have been cited as a reason for dissolving the Lower House to gauge public opinion on the matter.

The tax increase features in party pledges for the Upper House election. Abe is also expected to announce at the Group of 20 summit to be held in Osaka later this month that he will go ahead with the increase.