Sangma, first propped up by Tamil Nadu Chief Minister Jayalalithaa and her Odisha counterpart Naveen Patnaik, would arrive here tomorrow in the evening, a day ahead of the showdown on July 19.
The former Lok Sabha Speaker is likely to meet Jayalalithaa, expected to return here tomorrow from Kodanadu Hills where she is camping now, sources said.
Mukherjee, backed by almost the entire political spectrum, launched his campaign with much fanfare here on June 30 after calling on key UPA ally DMK president M Karunanidhi, whose party gave him a rousing reception.
The former Finance Minister, who enjoys a close rapport with Karunanidhi, had then said it was natural to start his campaign from here as DMK was a stable partner of UPA.
Sangma, also supported by BJP, has been on a whirlwind nation-wide tour seeking votes on the 'tribal' card though Mukherjee's win appears all certain.
Jayalalithaa has convened a meeting of her party MPs and MLAs at the AIADMK headquarters here tomorrow to fine-tune her party's preparations for the Presidential election.
The DMK MPs and MLAs met today where party chief M Karunanidhi asked the legislators to ensure the victory of Mukherjee.