It doesn't help Obama's case that his excuse is a sham. The Keystone pipeline had already been essentially cleared by environmental bureaucrats. Adding the pipeline from Alberta to the Gulf wouldn't scar some pristine wilderness, it would be more like adding just one more string to a spider web, given how many pipelines already crisscross the region.
Opponents say it would threaten the groundwater in Nebraska, where some 21,000 miles of pipeline already exist. But, as the American Enterprise Institute's Kenneth Green notes, any spilled oil would have to flow uphill to reach the Ogallala Aquifer.
Even the unstated but important motives driving opposition to the pipeline are hogwash. The environmentalists to which Obama is pandering have an understandable, if at times irrational, fear of oil spills and a religious faith in the dangers of global warming. The only problem is that blocking the pipeline will, if anything, increase the likelihood of oil spills because Canada will still bring the oil to market. But if it can't sell it to America it will sell it to China, which will bring it home via tankers, which spill more often -- and more calamitously -- than pipelines. Moreover, China will still burn the oil, meaning the effects -- real or alleged -- on global warming will be the same (or marginally worse, given the "footprint" of tankers). Also, the U.S. will still buy oil -- only we'll get more of it from the Middle East, again via tankers, deepening our dependence on their oil (another Obama bugaboo).
Theories abound as to what's going through Obama's mind. He wants to deny the Republicans a policy victory. He needs to build the case that the GOP is playing partisan games. He's an ideologue who, like his environmental base, just doesn't like oil. He honestly believes that the bureaucrats need to do yet another environmental study. He's bigoted against infrastructure projects that don't require government planning and taxpayer dollars (like Solyndra).
All of these explanations are plausible. And all of them highlight that his top, chief, first and number one priorities aren't what he says they are.