Mehboob Ali Qaiser, a former Congress state unit chief, said the conviction will have impact on the politics of Bihar "one way or the other".
"He is a strong leader of his party (Rashtriya Janata Dal). There is a sense of despondency in his party upon his conviction. But there could be crystallization of party's support base in the coming days," Qaiser said.
He said full impact will only be known after the sentencing of Oct 3.
Qaiser said that Congress had not yet made up its mind whether it will go alone in Bihar or forge a tie-up and Lalu Prasad's conviction could have a bearing on possible understanding with the RJD.
He said party vice president Rahul Gandhi's attack on the ordinance that could have helped Lalu Prasad retain his membership of Lok Sabha would influence the party's thinking towards its erstwhile ally in the state in the coming days.
RJD provides outside support to the Congress-led United Progressive Alliance government. The two parties have been allies in the past.
Congress sources said there were varied suggestions from party leaders in Bihar on alliances. They said while a section favours a tie-up with the RJD, another feels that the party will be better served if there is an alliance with the ruling Janata Dal-United.