No issue this side of the Keystone XL oil pipeline has been ruminated on longer by the Washington political set than immigration reform. So, President Obama knows what he is getting into when he officially announces his decision Thursday night to take executive action to halt the deportations of millions of undocumented immigrants. And he's doing it anyway. Why? Because he thinks he knows how, in the end, this all plays out -- and thinks it works in his favor.

Here's what Obama thinks he knows:

1. Republicans were never going to work with him.  You can imagine Obama rolling his eyes -- in private, presidents are formally banned from rolling their eyes in public, I think -- when Republicans in Congress talk about the well of bipartisanship being poisoned if he signs this executive action on immigration. In Obama's estimation, that poisoning happened long ago and, even after it happened, he was still willing to drink some of the water from the well. (Strained metaphor alert!) The idea that signing an executive action on immigration -- or doing anything else -- has some sort of chilling effect on bipartisanship is laughable to Obama. Bipartisanship has been dead for a while; all he's doing now is kicking the corpse a bit.

2. Republicans will overreach. By thumbing his nose at Republicans' warning on immigration, Obama knows he's provoking the other side. And, his expectation is that some of the louder elements within the GOP -- Ted Cruz, he is looking at you! -- won't be able to resist calling for his impeachment and the like -- the sort of thing that will take the spotlight off Obama and turn it onto a relatively small group of Republican elected officials who are not exactly the face the party wants to project to the broader public. The more angry talk comes from Republicans -- particularly if that rhetoric slips from being 100 percent Obama-focused to including Hispanics -- the better for Obama. One of the biggest problems he faces is that a majority of Americans (56 percent in the new NBC-Wall Street Journal poll) want Congress, not him, to set the policy priorities for the country. If Republicans radicalize themselves -- impeachment! government shutdown! -- in the wake of this executive action, Obama can make the "You want to trust these guys?" argument to the public much more easily.

3. He can and will sell it. As we've written before, Obama -- still -- has total confidence in his unique ability to convince the public that he wants to do the right thing. (Whether that confidence is justified is a debate for another blog post.) And so, the 48 percent of people in the NBC-WSJ poll who disapprove of him taking executive action on immigration (38 percent support it) doesn't worry him. Obama is convinced that another number in that poll -- 57 percent support a pathway to citizenship -- is more telling and important. The support for citizenship, which is not included in his executive action, is indicative, Obama allies believe, that the public supports the policy direction in which he is steering the country, even if they aren't sure they do yet. That's why Obama will be in Las Vegas on Friday to rally support for the move, and the White House is promising more events like it in the future. Of course, Obama's ability -- and willingness -- to sell his policy priorities has a decidedly mixed record of success.

4. The legal argument is too convoluted to matter politically. Obama, as you may have heard, is a constitutional scholar. He also knows most people in the United States, well, aren't. So, he believes that an extended debate in the public space about whether a phrase ("shall take Care that the Laws be faithfully executed") in Article II of the Constitution gives him the power to take executive actions isn't terribly likely. (Yes, constitutional scholars -- liberal and conservative -- will chew on this issue for days, weeks and maybe even months. But, per my point above, most people aren't constitutional scholars.) Obama and his team have gone over the legal justification for the move probably 100 times but it's unlikely that the fight over it will be, primarily, a legal one. This is a political fight -- and has been for quite some time.

5. It will energize and unite increasingly fractious Democrats in Congress. BREAKING NEWS: Congressional Democrats and Obama are not on the best of terms right now. And even more BREAKING NEWS: Congressional Democrats and other congressional Democrats are not on the best of terms right now. What better way to unite the clans, if you will, then to remind them of a shared enemy? For much of 2014, congressional Democrats (and the White House) seemed adrift -- without any sort of policy fight to engage in. Although executive action is not exactly a robust legislative battle -- it's actually the opposite -- Obama's move on immigration will give Democrats something to fight for that the vast majority of the caucus believes is the right thing to do. For a party in desperate need of a rallying moment, Obama believes this is it.

6. This will cement the Latino community as Democrats for a very long time. Hispanics -- and especially groups that advocate for the rights of undocumented workers -- won't get everything they want in this executive action. (A halt to deportation is not a path to citizenship.) But, this move coupled with Obama's executive order on DREAMers in 2012 allows him (and the Democratic Party) to make a very strong case that they are the only side in politics genuinely looking out for Latinos.  Given the massive growth in the Hispanic population and its slow-but-steady increase in political influence, locking down that voting bloc as solidly Democratic has vast long term effects on the country's politics.  And, don't forget -- because Obama definitely hasn't -- that for a president desperately in search of second-term legacy accomplishments, this is a big one.

Whether what Obama thinks he knows about the imminent fight winds up being right or wrong is the stuff of the coming weeks and months. But, he's gamed out what his announcement Thursday will mean and likes what he sees.

President Obama is set to announce an executive order on immigration, but how does that work? Here's a look at how the White House, Congress and the Supreme Court have roles — and limitations — in executive orders. (Julie Percha, Jackie Kucinich and Rebecca Schatz/The Washington Post)