Tun Dr Mahathir Mohamad, once the symbol of Barisan Nasional's (BN) unshakeable grip on power, has been campaigning for Malaysia's opposition ahead of two bellwether by-elections, the first time any former prime minister has openly done so.

Having led calls for Prime Minister Najib Razak to resign since the beginning of last year, Dr Mahathir went on the stump in both Selangor and Perak, hoping to deliver a body blow to the ruling Umno in the simultaneous votes on Saturday.

But the reception in coastal Sungai Besar last Saturday and Perak's royal town of Kuala Kangsar the next day was muted. Fewer than 500 people greeted him at each location, where he repeated calls to reject Datuk Seri Najib's leadership.

The Umno-led BN is set to coast to victory in both the largely rural seats, politicians and analysts say, helped by millions in handouts to voters and government promises of development projects. The split in the opposition is also helping BN.

To many voters outside the big cities, bread-and-butter and development issues - and not the scandal involving state fund 1Malaysia Development Berhad - take centre stage.

Dr Mahathir received another setback yesterday when a second letter by jailed opposition leader Anwar Ibrahim was made public. Like the first, the letter to Parti Keadilan Rakyat vice-president Shamsul Iskandar told him to exercise restraint and wisdom when dealing with Dr Mahathir.

The opposition candidates endorsed by Dr Mahathir could end up worse than just losing on Saturday. There is some expectation that the duo from Parti Amanah Negara might finish behind their former opposition partners from Parti Islam SeMalaysia.

If that comes to pass, it would reflect on Dr Mahathir's waning influence in the face of BN's gigantic election machinery, something that he used to wield so well.