Worried by promises from liberal U.S. presidential candidates that they will threaten to unilaterally pull out of NAFTA if certain protectionist changes are not agreed to, Ontario premier Dalton McGuinty made his case to preserve NAFTA in the Financial Times:

Canada is the largest trading partner for 36 of 50 US states. Pennsylvania exports more to Canada than its next seven markets combined. Cross-border trade supports 221,500 jobs in Michigan alone. The regional trade relationship is complex, dynamic and, ultimately, good for our shared economy.

We are interdependent. What is good for one is good for all. To go backwards, when competitors in the European Union and South Asia are becoming increasingly integrated and productive, would be a mistake. Canada and the US are joint stewards of a valuable economic partnership. But we are also stewards of something far more valuable — one of history’s great political friendships. For a century and a half, that friendship, in spite of the odd crack, has been a rock-solid example to the world. I believe our choice – the only choice – must be to deepen and strengthen our relationship so that we continue to grow, together. We owe nothing less to businesses and families on both sides of the border.