My colleague Allan Fotheringham nominates Clyde Wells as the ''most impressive'' politician on the national scene. As long as nominations are open, may I propose Frank McKenna as the most dangerous man in Canada?

The New Brunswick premier appeared Monday before the special Commons committee trying to save the Meech Lake Accord, chaired by the noted legal scholar Jean Charest. McKenna told the committee it is too late to change Meech. Whatever its faults, it had acquired a symbolism in Quebec that gave Robert Bourassa no room to accept any amendments. The best that could be hoped for now was to pass his companion resolution of post-Meech amendments designed to mitigate the accord's worst effects. Above all, ''we've got to cool inflammatory rhetoric! '' he said, banging the table.

It all read rather like a Globe & Mail editorial: the consequences of failure do not bear thinking about, so best not to think too hard about the consequences of passing it, either. It remains to be seen whether this will budge Manitoba and Newfoundland from their demands for changes to the accord itself. So with the deadline for ratification approaching, it's time to think the unthinkable. What if Quebec doesn't separate?

This is not to say that Quebec is bluffing; only that the set of calculations facing the Quebec government will change once Meech Lake is dead. It is notable how many people have forgotten the entirely rational basis, in the home of ''profitable federalism,'' for continuing negotiations in the wake of Meech's collapse. Once again it falls to me to put the case for complacency.

Meech is only a symbol for the people of Quebec so long as it is held out before them. Take it away, and it is no longer a factor. Once dead, it represents, as economists say, a sunk cost. It cannot be retrieved, so any constitutional calculation must be based on the profit and loss incurred from alternative courses of action from that point forward.

It's possible that Quebecers would be so outraged as to countenance separation. But remember separation comes at considerable cost: whatever its direct economic effects, it would involve at a minimum 10 years of difficult and testy negotiations to divide the assets and liabilities of Confederation, with much uncertainty over the outcome.

Confederation continues so long as both parties, Quebec and the rest of Canada, are better off together than apart. If the rest of Canada were truly saying ''no'' to Quebec, threatening its language and culture, then the costs of separation would probably be worth enduring. But since the rest of Canada is, in fact, anxious, even desperate to accommodate Quebec, stopping only at imperiling its own survival, this can hardly apply.

REJECT PARODY Every one of Meech Lake's major critics accepts every one of Quebec's initial five conditions for ratifying the 1982 Constitution. They simply reject the bizarre parody of those demands that appears amid much other useless clutter in Meech Lake. The day after June 23, Canada would be back offering everything Quebec asked for going into this round - perhaps more.

Everything we know about Quebec voters suggests they are supremely rational, contrary to the touchy, temperamental stereotype beloved both of anglo bigots and Uncle Toms like Jacques Parizeau. These are the people, remember, who elected both Pierre Trudeau and Rene Levesque. It is preposterous to think they would separate over whether, to take one of Meech Lake's many extraneous clauses, the first ministers should be condemned to perpetual annual discussions of the fisheries.

Would Quebec, short of separation, simply refuse to participate in further constitutional negotiations? Perhaps, for a time. But with the death of Meech, Quebec's ambitions within Confederation remain unfulfilled. Prior to the accord, it made sense to hold out, using the manufactured grievance of 1982 as a pretext. That gambit having failed, there are many items of great interest to Quebec on the constitutional agenda. It can sulk about and get nothing or it can come back to the bargaining table, and gain through exchange.

The very worst thing we could do at this point is to patch together another ambiguous mess in the name of keeping Meech alive, which I'm afraid is just what McKenna's proposal is. Meech Lake reduces both the costs of separation, since it would amount to independence in stages, and the benefits of Confederation, since it would yield at one go most of Canada's bargaining chips. It thus fatally alters Quebec's calculations in favor of the very outcomes it is intended to forestall. We can only hope, in the tense standoff that lies ahead, that cooler heads will not prevail.