Mamata Banerjee had gone to Patna in February this year when Nitish Kumar returned to power after ousting Jitan Ram Manjhi. (File photo)

A day after his huge win in Bihar, Nitish Kumar on Monday called up Mamata Banerjee to thank her for her support, but the West Bengal chief minister is not sure if she can go for the swearing-in ceremony of Bihar's new chief minister."When I went for his last swearing in, I had congratulated Nitishji for his next swearing in," Ms Banerjee said on the sidelines of a festive meet with industrialists in Kolkata. "I have some visits to the districts planned so let's see," she added. Mr Kumar is expected to take oath as chief minister sometime next week.The bonhomie between Ms Banerjee and Bihar's strongmen is being closely watched. Who will they support when Bengal polls next year is the big question. The Left has already launched the slogan "Modi Bhai Didi Bhai".CPM politburo member and Bengalks leader of opposition Surya Kanta Mishra tweetd saying, "#ModiBhaiDidiBhai 2sides of d same coin.She wl also face d same.Ppls averse to her anti-demo. soft communal politics. (sic)"CPM lawmaker Md Salim tweeted, "Bengal wl drive home #BiharVerdict over intolerance by rejecting @narendramodi & ousting fellow intolerant @MamataOfficial #DidiBhaiModiBhai. (sic)"Ms Banerjee had gone to Patna in February this year when Nitish Kumar returned to power after ousting his erstwhile protege Jitan Ram Manjhi.Ms Banerjee has advocated a federal front of regional parties against the BJP ever since she walked out of the NDA. So far, her efforts have not borne fruit.BJP chief Amit Shah had recently said that after Bihar the BJP would turn its attention to Bengal.However, as Rashtriya Janata Dal chief Lalu Yadav pointed out on Sunday, "BJP had planned to win Bihar and march to Bengal. We have stopped their march to Kolkata."Though the imminent threat of a BJP onslaught in Bengal has receded, speculation is on over which side the Grand Alliance will take in the state: Left or Mamata Banerjee.Janata Dal United's KC Tyagi is reported to have said they will support Mamata Banerjee in Bengal but also work with the Left in Delhi.If the Grand Alliance, which includes the Congress, backs the Left in 2016, Mamata Banerjee will have face a united Opposition. It may not change her party's electoral fortunes but could prove to be a serious irritant. A divided opposition has helped in the past.