President Obama’s executive action on immigration is coming—Immigration-palooza 2.0 is here—and Republicans won’t take it delicately. (Cue the Ron Paul “It’s happening” GIFs.) We’ve seen this movie before, and it isn’t pretty. Over the coming weeks, Republicans will unfold their strategy to push back against the president’s unilateral move, which could halt deportations for up to 5 million undocumented immigrants. It’s the first big fight of the new Congress, and the new Congress isn’t even sworn in yet.

The first thing to bear in mind with the coming immigration smackdown is that this isn’t the first time in recent memory that the Hill has fallen into mass chaos over immigration. Last year eight Republican and Democratic senators teamed up to introduce comprehensive immigration reform legislation intended to solve the increasingly pressing problem of mass illegal immigration. We all know how well that turned out: Conservative lawmakers and activists pushed back as soon as details of the bill started to emerge, Tea Party activists descended on Washington, phone lines melted, the bill passed the Senate on a 68–32 vote, and then the House did nothing and the legislation unceremoniously died.

Those days may soon return. Fox News has reported the president could announce the specifics of a long-vaunted executive action on immigration as early as next week. There’s a host of proposals that he’s theoretically considering, including a possible expansion of a previous executive action that kept some immigrants who entered the United States illegally as minors from being deported. Another potential provision of the president’s executive action, per Fox, is to expand programs that end deportations for some undocumented immigrants whose close relatives are in the United States legally. That wouldn’t be Obama’s first executive action to prevent deportations; in June 2012 he moved to stop deportations of some undocumented immigrants who entered the country as minors.

Democrats have been largely unified in lauding the president’s decision to move forward without Congress, and no prominent members of his party have suggested that he lacks the authority to do so. And advocates of immigration reform will be disappointed only if the scope of the president’s action is narrower than expected.

Republicans, however, are in an entirely different boat. For this to make sense, you have to understand that the GOP is about as divided over immigration policy as any political party is over any single issue. There’s a general consensus that the border should be secure and that amnesty is bad, but things break into a million tiny pieces from there. Depending on whom you ask, “border security” can mean a host of different things, including fence-building, higher security spending, more Immigration and Customs Enforcement officers, and who knows what else. And the word amnesty is also ambiguous: Sen. Marco Rubio, one of the Senate immigration bill’s original sponsors, means something very different when he uses that word than immigration hawk Sen. Jeff Sessions. There are Republicans who want to put the millions of undocumented immigrants in this country on track to getting citizenship, and there are Republicans who want to send everyone back to their home countries as quickly as possible and seal the border behind them.

If you want to get a better sense of how this tension plays out, you should watch this debate that Americans for Tax Reform President Grover Norquist and columnist Ann Coulter—nobody’s RINOs—had on CNBC during the last immigration fight. If you want another example of immigration tearing into the roof of the GOP, then recall the events that led to former House Majority Leader Eric Cantor’s astounding primary defeat. Dave Brat, the political newbie who beat him, had basically zero powerful backing except from national anti-immigration reform figures (including Coulter and radio host Laura Ingraham). And if you still aren’t persuaded, do a quick perusal of Rubio’s rise and fall in Tea Party circles. The Florida senator came to Washington as a Tea Party golden boy but saw his presidential prospects tanked by the time the immigration kerfuffle resolved itself. Now, that doesn’t mean he can’t run a competitive presidential campaign and will never get conservative grassroots support. But it does mean that there’s a sizable, powerful chunk of the conservative base that will never trust him because of his stance on immigration reform. You can’t overstate the extent to which immigration turns Republicans against Republicans.

With that in mind, the big question is this: How will Republicans respond to the president’s impending move?

And to answer that, it’s important to bear in mind that there are two separate grievances that Republicans have with the president’s coming executive action.

The first grievance is with the substance of the president’s anticipated move. The Ann Coulter wing of the GOP—for lack of a better term—worries that increased immigration will depress wages and increase the strain on the social safety net. These conservatives argue the president’s executive action will incentivize illegal immigration and exacerbate a variety of social ills. Not all Republicans make all of these arguments, but many do, including Sessions, as well as numerous members of the House Republican Conference.

The other main grievance has less to do with the substance of the action than with the fact that the president is taking it unilaterally. Many Republican leaders (including Sessions) see the move as an unconstitutional power grab that threatens our system of checks and balances. Numerous voices on the right have expressed this concern, including Charles Krauthammer, who said the president’s move could be “impeachable” and “a flagrant assault on the Constitution.” And in a Politico Magazine op-ed, Sen. Orrin Hatch argued that by unilaterally changing the way immigration laws are enforced, the president has “failed to live up to his constitutional duty to ‘take Care that the Laws be faithfully executed.’ ”

Some Republicans are in the first camp, some are in the second, and some are both.

Republicans have a number of options, none of which comes close to guaranteeing their desired outcome. First off, House Speaker John Boehner has floated the possibility of suing the president over his move. According to the Washington Post, Boehner is considering either expanding his current lawsuit against the administration that focuses on the implementation of the president’s health care law, or launching a second one on immigration. This option seems premised on the idea that suing the president is a muscular response that would mollify the speaker’s angry base. That premise is also probably false. One Senate aide who focuses on immigration said a lawsuit on the issue could be stuck in court for years. And the speaker’s health care lawsuit has drawn great mirth from some quarters, as both the law firms he hired for the project have quit. There’s also some question as to whether Boehner even has legal standing. Breitbart, which is probably the favorite news site for anti-immigration-reform activists, dubbed Boehner’s lawsuit idea a “clown show.”

But that’s obviously not the only option. Another possibility is trying to defund the president’s move. If that gives you flashbacks to a government shutdown, well, it should. Congress will need to authorize more spending in early December to keep the government running, and some conservatives have suggested putting a provision in the next spending bill to specifically state that the president isn’t authorized to use funds for his new immigration action. The next spending bill (called a continuing resolution) could be either short-term or long-term.

Another possibility: buying themselves a little time. Republicans could pass a short-term spending bill without anything on immigration enforcement, and then pass a long-term spending bill next Congress—when the new members are sworn in and they control the Senate—to try to limit his authority on the issue.

Defunding the president’s immigration gambit could come with some hiccups, though. First, it’s not crystal clear whether the president’s immigration action would be funded by fees or through the appropriations process. People I spoke with didn’t have a definite answer to that question. If the former is the case, then it might not be possible to use a spending bill to block the president.

Second, there is a reasonable chance that the president wouldn’t be interested in signing a spending bill that put him in those constraints, in which case the government could run short on money and—ta-da!—shut down.

Nobody wants a shutdown. Boehner doesn’t want it, incoming Senate Majority Leader Mitch McConnell doesn’t want it, House Republicans don’t want it, even hawkish immigration activists say they don’t want it. One would hope that means it’s very unlikely. One would hope. But if the president didn’t sign a spending bill that funded everything but his executive action, his party could face substantial political consequences.

Republicans don’t have an ironclad plan for responding to the president’s move yet. All of this is very theoretical, and it could change depending on what specifically the president decides to do.

Either way, expect to hear a lot from Republicans about “poisoning the well.” Moderate Republican senators who spoke with Slate on Thursday reiterated (and re-reiterated) that a well would be poisoned if the president moved ahead with his immigration action. The implication is that there’s currently a metaphorical well of pristine water symbolizing the promise of cooperation and bipartisanship in the next two years of the Obama presidency. (The White House likely isn’t aware of this well’s location.)

The bottom line is that comprehensive immigration reform is a huge issue for conservatives of just about every stripe. A number of Republican candidates made opposition to comprehensive immigration reform central to their election campaigns, including Sens.-elect Thom Tillis and Tom Cotton. They will not want to “go soft” on immigration within minutes of arriving to their new offices. Many Tea Party activists thought the Senate Gang of Eight’s immigration bill was just as bad as Obamacare, so they will be riled up from Day One. In a sense, the immigration debate conjures something close to two unstoppable political forces: The activists who favor comprehensive immigration reform get at least as galvanized as the activists who oppose it, and both groups are integral parts of the Democrats’ and Republicans’ respective bases.

So here we are. The 114th Congress will get off to a rollicking start. Just be sure to keep an eye on your well water.