Mr. McGuinty responded by suggesting he was not banking on Mr. Martin's $9-billion health care plan -- the centrepiece in his platform -- as it was just "a campaign promise." Mr. Martin raised the ante, insisting that a politician should only promise what he can do, and "whatever you say you're going to do, do." Stung, Mr. McGuinty chose this week to announce that he would bring in a bill setting fixed election dates, so that "never again will a premier have the ability to set election dates when it is politically opportune for the government." Wait a minute: are you saying that Mr. Martin... ?

All hugely entertaining, as I say -- almost as good as the debate between Jean Lapierre and Jean Lapierre. But not so much fun for Mr. Martin. Things had deteriorated to such a point that by week's end the Prime Minister was forced to issue a new promise: that he would keep his promises. If he had not kept at least three of them within two years, he told reporters, he would resign. This raises all sorts of interesting epistemological questions. What does he do if he doesn't keep that promise? Kill himself?

But to be serious for just a moment: How do we hold politicians to their promises? Mr. McGuinty's decision to break his promise has caused such outrage precisely because he went to such great lengths to convince people he would not: signing the Canadian Taxpayers' Federation pledge, repeating it over and over again in television ads, in words that left no room for interpretation. As a political friend of mine puts it, there are lies, and then there are lies. And after all, he was really committing himself to nothing more than obeying the law: Mr. McGuinty "broke faith" (Mr. Martin's words) not by raising taxes, but by doing so without first holding a referendum, as required by the province's Taxpayer Protection Act.

Similarly, the Balanced Budget Act did not outlaw deficits altogether: it merely stipulated that in the event, the cabinet should take a cut in pay. Mr. McGuinty did not amend the law to allow the government to run a deficit, but rather to assure that he and his ministers should not have to bear the consequences (beyond the first year, when to their credit they did).

So we are left grasping at air. If politicians can simply change the law, post-election, by which the voters were assured they would keep their word, pre-election; if the penalty prescribed for breaking a promise is itself among the promises broken, then what are we to do? Perhaps we should insist they post a bond, the money held in escrow until the promises are fulfilled.

Or perhaps we need a different kind of law: one that would focus on the truth or falsity of claims made in the course of the campaign, rather than on actions taken or not taken once in government -- a "truth in advertising" law for politicians. In the current example, Mr. McGuinty would be liable, not for running a deficit or raising taxes as such, but for promising he would not. Indeed, the CTF thinks it has a case against the premier under existing law, claiming it had a legally enforceable contract. We'll see.

Comparisons are often drawn with the private sector, not least in this column. If a company issues a prospectus, for example, it must provide "full and fair" disclosure. It doesn't have to outright lie to run afoul of the securities laws: it's enough if it is even misleading. On the other hand, even in the private sector, there are lies and then there are lies. If every suggestion ever made or implied in an ad were required to be literally true, the entire advertising industry would collapse. Advertisers, like politicians, are indulged a certain poetic license.

But if you say your product contains an ingredient it doesn't, or that it doesn't contain something it does, you will face legal penalties, and it seems to me the same ought to apply in political life. That's the difficulty: How to design a "truth in politics" law that would separate ordinary bits of hyperbole from specific, verifiable statements that are intended to be taken as the literal truth?

Perhaps we should let the politicians themselves decide. For the most part, their campaign utterances would remain immune from the law's scrutiny, and would be received with according degrees of skepticism by the public. But where they wished especially to be believed, they could "opt in" to the law, declaring this or that statement to be made under its provisions -- rather like swearing an oath in court. Of course, the question would immediately arise why they did not make all of their promises in similarly binding terms, and why all candidates did not do the same. Exactly: like Gresham's law in reverse, good faith would drive out bad.