ISTANBUL — Heating up the campaign for the coming parliamentary elections, Turkey’s governing party on Wednesday unveiled a proposal to build a canal parallel to Istanbul’s Bosporus..

Details of the plan, which has been speculated about privately in recent months as the “crazy project” of Prime Minister Recep Tayyip Erdogan, had been kept under wraps, but on Wednesday it immediately became the centerpiece of his party’s bid for a third term in power.

The pro-Islamic Justice and Development Party, known as the AKP, foresees a 28- to 30-mile canal connecting the Black Sea in the north to the Marmara Sea in the southwest that would be a safer alternative for heavy tanker ships than the natural Bosporus straits, which run through the heart of Istanbul, a city of around 15 million people.

The plan aims to divert ship traffic along the Bosporus that sometimes numbers 149 tankers a day carrying natural gas, crude oil, chemicals and other industrial goods.