Likud presidential candidate MK Reuven Rivlin is expected to distribute a letter today attacking his main rival for the post, Vice Premier Shimon Peres.

In his letter to the other MKs, Rivlin warns that electing Peres will not contribute to restoring the institution's public standing. The letter does not mention Peres by name, but it leaves no doubt that he is the subject.

"A blatantly political selection will transform the presidency into just another political position, and turning the presidency into a prize for lifetime achievement, or political compensation for past disappointments, will undermine the restoration of the presidency's public standing," Rivlin wrote.

Meanwhile, Peres is expected to announce his candidacy this morning, during a special gathering of the Kadima faction.

Prime Minister Ehud Olmert told Kadima MKs that electing Rivlin would serve only to strengthen Likud and MK Benjamin Netanyahu.

Olmert has promised Peres that he will put his full weight behind him.