Obama knew this. He is also the most political president in living memory. He brings political advisers to national security briefings. There is no way he cannot be aware of the political ramifications. Further, his executive order will expire in three years unless the next (Democrat) president renews it. So we must believe that he care more about creating a wedge issue for Democrats to exploit in the coming elections.
So, where is President Obama? He talks like an Altruist but consider the long-term effects of his executive order. He strengthened the Hard Core. Now, in addition to their previous arguments, they will also complain that any legislation remotely like Obama's executive order will reward presidential overreach. Further, and Republican Realist who supports any form of immigration reform will be challenged from the right in the primaries.
The final group is the Cynics. They talk like the Altruists but they have no intention of actually passing immigration reform. They have calculated that the Democrats will do better with the Hispanic vote as long as immigration is still an issue. They are the reason that immigration was never even brought up during the period that Democrats had complete control of Congress.
The third group is the Altruists. They want a blanket amnesty regardless of the consequences. They are the reason that we call illegal immigrants "undocumented". They are mainly Democrats who expect that passing an amnesty will guarantee the Hispanic vote for the foreseeable future and they plan on scaring Hispanics with deportation if the Republicans get their way.
The second group is the Realists. They admit that deporting millions of people would be both cruel and harmful to our economy. At they same time, they are very aware that the amnesty offered under Reagan didn't work. They want a balancing act that provides a path to citizenship but does still rewards legal immigrants. They also call for stricter enforcement. This group is mainly made up of moderate Republicans who see immigration as loosing issue for Republicans and want it resolved.
There are basically four camps on the immigration debate. Understanding them is core to understanding President executive order on immigration.The first group is the Hard Core. They rightly point out that illegal immigrants are, in fact, here illegally and they worry that anything short of deportation will reward lawbreaking. They are rabidly against anything that remotely sounds like amnesty. While this is the position of the Tea Party, the faction predates it by years.