There are several reasons due to which the concept of Third Front would not only remain a mirage but would always be a disaster every time they come to power by default. The last decade of the twentieth century had witnessed several such third front kinds of dispensations coming to power with external support from Congress. On each occasion it was a nondescript regional leader with no national appeal or support being propped up as a Prime Ministerial candidate. And on each occasion the net result was not just an unstable government at the centre lasting barely a few months but also resulting in a radarless India faltering on every front with no concrete or defined policy initiatives. The short lived Prime Ministers played peaceniks and destroyed much of India's clout in South Asia even while on economic front, populist measures and lack of courage, political will or clout to take hard decisions created much void. It is not to say that last ten years of UPA rule has been much better but fact remains that even coalition politics play well with a mother ship or say a national party leading from the front with smaller but important allies riding on her back.
There is no doubt that the regional parties are a strong political force in the country today and their existence as well as the era of coalition politics is here to stay. But most of the regional parties, even when they have reasonable hold in their own region, are almost irrelevant in most of the other parts of the country. Secondly, most of the regional parties are essentially driven by either a single family or a personality each of whom have their own ambitions to take the top job. Therefore, Third Front is essentially a ship with too many aspirants for the Captain's job. Moreover, knowing that their own area of influence is limited, each of the regional parties prefers to cater to their own constituencies rather than have a national view of things. For the Tamil Nadu based parties, for example, Sri Lanka is a sensitive issue which may not be that big an issue for the rest of the regional parties. On economic and foreign policy issues as well many of them have completely divergent views.
Third Front would not only remain a mirage but would always be a disaster
Additionally, it has always been witnessed that most of the regional generally have a tendency to sway towards either of the two national dispensations, each led by BJP and Congress, after the general elections, even while making overtures towards a Third Front kind of a formation before elections. On most occasions, this has been a ploy to put pressure on the leading parties as a bargaining chip. Thus, even while an increasingly irrelevant Left dispensation, made all the more irrelevant by the emergence of left of the centre AAP kind of party and TMC's complete dominance in Bengal, makes effort to stay afloat in terms of relevance through drastic efforts for a possible Third Front, it is for sure that most of the heavyweight regional parties including the likes of Biju Janata Dal (BJD), AIADMK, Teleu Desam Party (TDP) and even TMC would keep their options open and would not reveal their real motive till the elections are over and a general picture is available. There is a high possibility of many like AIADMK, BJD or TDP and TMC making a move to support BJP in case it comes to striking distance of making government in the centre.
There is also no doubt that regional parties like JDU and RJD in Bihar or Samajwadi Party and Bahujan Samaj Party in UP or say DMK and AIADMK in Tamil Nadu or TMC and CPM in Bengal never see eye to eye and thus even when they are strong regional forces on their own, the possibility of SP and BSP or JDU and RJD or AIADMK and DMK coming together to sail on the same boat is highly unlikely. Each of them would thus prefer to support a national party more than supporting each other.
Thus, hype around Third or the Fourth Front or the enthusiasm of some to provide an alternative notwithstanding, it would essentially remain a myth or a disaster at best for India. It would always thus be better for India to be led by a national party than a coterie of regional parties coming to power on their own and pulling the nation and each other in different directions.