After BJP formally split with allies Janata Dal(U) and Shiv Sena over the presidential election, finance minister Pranab Mukherjee's candidature on Thursday also divided the Left with CPM and RSP deciding to support him, while CPI and RSP opted to sit out the July 19 poll. The BJP-JD(U) divergence is expected, but the formal articulation of positions served to again underline Bihar CM Nitish Kumar's insistence that BJP rule out Gujarat strongman Narendra Modi as a prime ministerial candidate.