Step back and the picture becomes clearer. The results of the recent by-elections to 31 Assembly seats spread across seven States confirm some of the key trends that emerged in the 15th Lok Sabha election. The Congress is gaining strength in Uttar Pradesh, the Left is losing its hold in West Bengal and Kerala, and the Bharatiya Janata Party is struggling in most places. But step closer and the details reveal other, smaller trends, different from those seen in the Lok Sabha election. Most notably, in Uttar Pradesh the Bahujan Samaj Party, which fared poorly in the 2009 Lok Sabha election compared to its performance in the 2007 Assembly contest, is recovering lost ground. (An alternative explanation: an Assembly election is not a parliamentary election.) The Congress is eating into the vote share of the Samajwadi Party, which got the largest number of seats, 23 of 80, in the Lok Sabha election. The BSP has gained at the expense of not only the SP but also the Congress. In the Firozabad Lok Sabha constituency, the Congress came out on top. The SP lost all the five Assembly seats it held, besides Firozabad. The BJP surrendered two seats, and the Janata Dal (United) one. The interesting question now is whether U.P., one of India’s most politically fragmented States, will see a polarisation between the BSP with Mayawati at the head and the Congress with Rahul Gandhi as the star campaigner.
West Bengal and Kerala saw the Left suffering big reverses in the Lok Sabha election, and the Assembly by-elections have confirmed the trends. The Left parties combined could pick up only one of the 13 seats they contested. Of the 10 seats in West Bengal, the Trinamool Congress won seven, the Congress one, and an Independent one. In Kerala, the Congress bagged all three seats. Maybe the numbers do not tell the whole story. In the eastern State, the Trinamool already held five of the seven Assembly constituencies and the Congress lost one of the two it held. The net loss for the Left was two. In the southern State, all three constituencies were held by the Congress, and are counted as the party’s strongholds. But this may also underestimate the erosion of popular support for the Left. With the Communist Party of India(Marxist) failing to win a single seat, the results must be extremely dispiriting for the Left. Sharp swings in the popular mood in a short time span are not unknown in Indian electoral politics, but as of now everything points to a change of regime when the two States go to the polls in 2011. Alternation in office may be accepted as the norm in Kerala — but an electoral defeat could be quite traumatic for the Left in West Bengal after a record 32 years in power.
Keywords: Congress, Left Parties, BJP, assembly by-elections

Comments:
A layman like me may perhaps not be able to analyse the results so deeply and clinically like you have done.But by and large,I would say the trend is somewhat indicative of the following:-
a)The BJP's fortunes are on the downswing.This was to be expected given the internecine fights we have been witnessing during the last few months starting with the parliamentary election debacle followed by the rebellion from senior party members with the crowning capitulation drama in Karnataka.
b)The Left,it appears,is going to be left by the roadside.Their regressive politics coupled with support to a corrupt Vijayan in Kerala and the repressive measures adopted in West Bengal and the
severe blow to to a belated attempt to woo the industrialists to the state coming a cropper are sure to have a terribly telling effect on its fortunes.
c)The Congress is slowly but surely regaining lost ground all around
and can look forward to weathering all storms comfortably for next few years.Only they should stop having any truck with opportunists like Lallu,Paswan,Mulayam and their ilk who are out to feather their nests no matter at whose expense.
d)Regional parties may gain importance.But if they too indulge in
politics of opportunism,they may be cast aside by the intelligent electorate.
Ovearll, Congress is gaining ground in all the states. It is time for the Left to change their thinking and actions in the information world.