Speculation on whether Samajwadi Party (SP) supremo Mulayam Singh has formally joined UPA emerged after he was seen seated to Sonia Gandhi's right at the high table at the UPA II's third anniversary dinner. UPA sources have said that Mulayam being seated to Sonia's right is a message that SP is firmly with the Congress and that now it is almost certain that SP will back the Congress candidate in the Presidential polls.