Promoters of the Keystone pipeline have done a good job making the project synonymous with jobs. In that way, to oppose it would be to oppose jobs. However, in Montana, the claim was suspect back in 2012 at the nadir of the great recession, and remains so today. The reason is that the pipeline is traveling through a portion of the state that already has very low unemployment, on account of there being very few people who live there. Thus, people would have to move to the area to achieve the employment provided by the project. And if we're talking about jobs in far eastern Montana available to young men willing to move, well...those already exist in droves.
Here's a map I put together in 2012. The numbers remaining basically the same.