THE way in which political parties are realigning themselves is bringing the day closer when the Congress may shed its inhibitions and makes a bid to topple the Vajpayee government. Old Congressmen are returning to the fold. The caste-based populists, who suffered a crushing rejection by the electorate when they were part of the United Front, are in search of new allies: Laloo and Mulayam Singh Yadav have not only forged an alliance with each other but also with the Congress. Earlier this week, Smt Mayawati of the Bahujan Samaj Party decided to back the Congress despite the presence of Mulayam Singh in its fold. And with the DMK getting palpably closer to the BJP, the Left Front has overcome its scruples about supporting the Congress if it consorts with the AIADMK. The stage is, therefore, set for a challenge to Mr Vajpayee.