On the face of it, the Bharatiya Janata Party should only be cheerful about its resounding victory in the Assam Assembly elections. In all the other states that went to polls this year – Tamil Nadu, Kerala and West Bengal – its seat tally will be in the single digits. But even looking at it from that perspective is a reflection of how much the BJP has grown over the last five years and the corresponding contraction of the Congress.

For the longest time, the BJP was a Hindi heartland party that had to rely on allies for it to expand to states outside the region. The party's win in Karnataka in 2008 was a landmark moment, when it formed the government in a South Indian state for the very first time. Narendra Modi's elevation to the prime ministerial position in 2014 – and the massive amount of votes he managed to pull in across the country – gave the party hope that it could use his popularity to expand into uncharted territory.

The party's setbacks in 2015, losing Delhi and Bihar, did not dent this vision since those were states where the BJP has a relatively strong presence and will continue to be influential players. A failure to make a mark in the 2016 elections would have been much more troubling, since all the states in contention were outside the traditional comfort zone for the BJP.

Assam offers a clear victory for the party, where its vote share, which was stuck around the 10% mark over the last decade and a half, has now jumped dramatically up to around 30%, as per trends on Thursday afternoon. Though the final numbers are yet to be announced, the party is likely to around 89 seats and form the government.

This would be the BJP's first victory in a state not just in the North East but anywhere in eastern India. While conditions in Assam aren't identical to those in the other North East states, it will boost the morale of workers across the region and opens the gate to expansion.

Nearby in West Bengal, the BJP has similarly seen a noteworthy jump in its vote share in West Bengal, from as low as 2% in 2006, to more than 10% this year. Although this has only turned into two seats, it creates a base for the party to build on in the future.

The same template applies in Kerala, where the party has only won one seat, when it was hoping to pull in at least four and as many as 10. But the BJP has always underperformed in Kerala, a state which has the highest number of Rashtriya Swayamsevak Sangh shakhas and a strong Hindu identity.

Through the last two decades, the BJP's vote share in the state has hovered around the 5% mark without having much of an impact on the state's overall politics. This time around it has leaped up to more than 10% – and this has even more of an impact than a similar vote share in West Bengal.

That's because Kerala has swung back and forth between the Congress-led United Democratic Front and the Left's Left Democratic Front for two decades now, with little in the way of a third option. The BJP has now cracked open a window into the state's political edifice, pulling votes from across the state even if it wasn't able to concentrate them enough to win many seats. It is now on track to disrupt the traditionally bipolar polity.

If the BJP is able to build on its organisational structure in the state, which will undoubtedly come under stress if the Left brings back its political violence, then it could be on track to be an even more influential player in the southern state's politics.