It is now clear that the most potent political force in the 2014 parliamentary poll will be AAP and the least potent, Congress. However, at this point of time, BJP is the most formidable party with considerable lead over the rest.
AAP is like a gathering storm over the whole of the country sending ominous signals to BJP and most other political parties to urgently and thoroughly reform their political outlook and culture. The storm is likely to get stronger and peak at the time of election resulting in AAP replacing Congress  as one of the two strongest political parties in the national arena, the other being BJP.
TOI poll confirms that 44% of respondents in 8 metros would vote for AAP and 25% want Kejriwal as PM. Albeit, 58% still want Modi.

I have tried to indicate the region wise opportunity area for the parties with a special mention of the north east for AAP, in my article on 23rd December, 2013 and the strong likelihood of continuance of AAP govt. in Delhi at least till election, in my article on 1st January, 2014 (Read: AAP vs BJP: Prospects and some issues)

The storm will further strengthen if their continuance in office is accompanied by a reasonably creditable achievement in such a short period of time. To counter it, BJP will also need to enhance its performance in BJP state governments. But even more than that BJP will need to convey that they are as keen as AAP in ushering an era of clean politics and performing governance at par with sensitivity to people's needs. It is a tall task given its past baggage and in this regard AAP may steal a march over BJP. But BJP has a much stronger organizational base, an immensely important factor in election, than AAP. Ultimately, it will be a leadership battle in terms of conceptualization, communication, organization and delivery skills.

BJP's strategy and philosophy will undergo changes because of AAP factor, even before the election. It will have to try projecting clean image and may field new younger candidates and have to cope with disgruntled discards, the deadwoods and tainted.

AAP has high hopes in Delhi and Haryana. BJP is expected to hold sway in MP, Rajasthan, Chhattisgarh, Goa and Gujarat. It has hopes in Himachal Pradesh, Uttaranchal and Jharkhand.

The most difficult state for BJP will be Karnataka because of Yedurappa factor and considerable AAP inroad.

In Maharashtra Sharad Pawar, Praful Patel led NCP is likely to be affected by the rising AAP philosophy and Shiv Sena & MNP, due to internal bickering.  BJP & AAP are likely to step in to fill this vacuum.

In UP, SP seems to be losing muslim support giving growing space to AAP. Crucial thing here is whether caste is losing its stranglehold especially among the backward castes? However, dalit votes still are with BSP. But on performance and honesty scale neither SP nor BSP fares well. This too may allow space for AAP. But BJP may eat into the backward castes votes; Bajrang dal and Durgavahini have strong roots in backward castes.

In Bihar, LD and LJD will face erosion from AAP and therefore BJP may have an edge.

In Odisha, BJD is expected to prevail over the challenge of BJP and considerable inroad of AAP.

South is more complex; Telengana is a huge factor. Regional players will call the shots in Andhra and in Tamil Nadu rivalry between Jayalalitha and Karunanidhi will intensify. AAP may make marginal inroads in Kerala.
Left's support base will shrink everywhere. Swearing-by-book ideology will receive a heavy blow. Congress & Left will be the most emaciated parties. AAP will tone down its high pitched rhetoric.

Notwithstanding the current lead of BJP, the emergence of AAP makes it very difficult for it to get absolute majority and therefore there will be a need to form a coalition and BJP will have to court the regional parties. Here it is reasonably expected that SP, RJD and communist parties remain natural allies of Congress.

One interesting possibility in this connection is that AAP, if does remarkably well, may also need coalition to form govt. It may appear difficult because AAP can't ally with corruption and arrogant political culture. But on a closer look, Mamata and a few others may emerge possible allies because of their better images and stronghold over relative populace.

Take Mamata in West Bengal for example. Her incorruptible image, concern for common people, sincerity, anti-nuclear stance and administrative and political acumen proved in introduction of administrative Calendar and handling of Darjeeling hill and Jangalmahal makes her very acceptable as an alliance partner. She, again, needs centre's co-operation. On the other hand, for fear of irking big segment of muslim voters, she would rather avoid any association with BJP.

Similarly, common ground can be discovered in Odisha and Sikkim where CMs have good images and the north east where BJP has little influence. Ultimately, AAP and these all may have a common approach for corruption free, common people and development oriented governance.

Last but not least, as the CPM and SP sponsored third front is no more likely to be an alternative, the sponsors themselves will be eager to ally with AAP. Having his ambitions for the post of PM thwarted, Nitish may offer support to AAM. Only time will tell what happens then.