Thiruvananthapuram,  No doubt, Kerala Chief Minister Pinarayi Vijayan is the tallest leader in the CPI-M and has proved himself as the most successful party secretary after being at the helm of affairs for 17 years.

But now Vijayan is preparing to face what could be his most testing moment in a glorious political career, since the assembly elections are round the corner.

One reason why the coming weeks would be crucial for Vijayan is that he is definitely treading in unfamiliar territory of having to lead his party to one of the most keenly awaited electoral fights with the traditional rival: the Congress-led UDF.

When the state went to the polls in 2016, it was never mentioned that it was Vijayan who will become chief minister, should the Left win the polls. As any political student in Kerala would know, the star campaigner then was none other than Vijayan's bitter foe for many years and his senior in the party, V.S.Achuthanandan.

Practically every candidate who contested the polls then, had the picture of the veteran former Chief Minister and hugely adored Communist Achuthanandan in all their campaign material and despite his advanced age, every Left candidate was desperate to get the veteran at least for one of their election meetings in their constituency. At that time, not many were keen on Vijayan, as his tough demeanour and body language was not the right one for a candidate, seeking votes for his/ her victory.

Once the votes began to be counted Vijayan grew in stature and prominence. Though Achuthanandan had high hopes, the announcement came that Vijayan would be given the chair of the Chief Minister.

The only solace Achuthanandan had was that the party decided to give him a cabinet post and made him the chairman of the Administrative Reforms Commission, which came with all the paraphernalia of comforts.

But now things are different. " Yes, will be an acid test for Vijayan, as it's he who has become the campaign leader. Achuthanandan for all practical purposes is not seen in the public domain for a long time, as he is 97 years old. This is perhaps a new challenge, which Vijayan has not faced as yet," said a CPI-M leader who did not wished to be identified.

A top Congress leader said it's make or break time for Vijayan, as he thinks that the recent local body polls which went his way, will be repeated in the assembly polls, but assembly and local body polls may turn out to be like chalk and cheese.

"The Kerala electorate is known for their electoral acumen, when it comes to pressing the button on the voting machine, as they think differently when it comes to Lok Sabha, assembly and local body polls. Vijayan is certainly on the backfoot, as Achuthanandan, their all time biggest star campaigner will not be seen for the campaign. The Congress has a few star campaigners, who certainly have started drawing huge crowds, as was seen in the ongoing statewide yatra of Leader of Opposition Ramesh Chennithala," said a Congress leader.

However, Vijayan is optimistic about rewriting electoral history by becoming the first chief minister in the state to retain power in an assembly election, even as the Congress appears to be on a strong footing as voters may choose the party in the light of Vijayan's perceived "arrogance."