That was part of it. The Mulroney government was forged by the bridging of Alberta conservatives (their traditional political base, along with fiscal conservatives in Ontario and the Atlantic) and soft nationalists in Quebec. Both groups thought they would benefit from a government that preached devolving powers to the provinces.

The failure of the Meech Lake accord certainly contributed to the collapse of one of those pillars. Lucien Bouchard represented the Quebec wing of the PC party, acting as Mulroney's Minister of the Environment. After the collapse of the Meech Lake accord, Bouchard along with several other prominent PC and Liberal MPs formed the Bloc Quebecois. Neither the PCs nor the current Conservative parties have ever reclaimed a significant presence in Quebec.

The Albertan pillar was undercut by the advance of Preston Manning's Reform party. They were unhappy with the attention paid by Mulroney's PCs in the Meech Lake Accord, and the fact it ignored many concerns that affected Western Canada, like senate reform. So Reformers weren't upset by the Accord's failure, as the content of the accord itself. That said, Reform didn't gain much widespread support until the PCs imposed the GST. Many Albertan voters resented a perceived lack of fiscal discipline from the PCs, and imposing a sales tax was particularly unpopular in Alberta, as there was (and still is) no sales tax at the provincial level there. So the GST was seen as a net new tax, as opposed to the tax increase perceived in other provinces. Additionally, the GST was originally blocked in the Sentate, but Mulroney simply appointed additional senators to get the bill passed. This served to underline the Reform party's criticism of the Senate as an institution.

To be overly reductionist, the failure of the Meech Lake Accord lost the PCs support in Quebec, and the GST lost the PCs support in Alberta. These issues led to the rise of the Bloc Quebecois and the Reform party respectively.

Source: Peter Woolstencroft 'Doing Politics Differently': The Conservative Party and the Campaign of 1993."