The threat of a government shutdown in December is getting real. Funding for the government runs out on December 8, but with Congress focused on the tax bill that President Trump wants delivered by Christmas, it’s unlikely that lawmakers will be able to agree on a budget for 2018 before the deadline.

The likely outcome is another short-term continuing resolution in early December that funds the government until the holidays – and that’s when things could get interesting. Here are three issues that could result in another shutdown:

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1. A DACA fix. The Deferred Action for Childhood Arrivals program will expire in March under an executive order from President Trump. Democrats want to restore the program’s protections for hundreds of thousands of people brought to the U.S. illegally as children, and they appear willing to use DACA as leverage in budget negotiations, with many threatening to withhold their votes for a spending bill if the immigration issue isn’t addressed in December. But party leaders reportedly are also worried about being blamed for a shutdown. Many Republicans want to handle immigration issues in a separate bill, with some looking to push the issue into 2018. “Privately, both sides are worried — fearful of either enraging the party’s base or getting punished at the polls for a government shutdown,” Politico reports.

2. Spending levels. Republicans have called for defense spending for 2018 that is $77 billion over the budget cap for 2018, but they need Democrats to agree. Democrats, however, want to see domestic spending increase by an equal amount, an option that is anathema to many conservative lawmakers. Failure to make a deal on raising the caps could bring us to a shutdown by the end of December as the continuing resolution expires and both sides dig in their heels.

3. A Trump tax mess. What happens if Republicans can’t pass a tax bill by the end of the year? Budget expert Stan Collender says it’s “easy to imagine Congress unable to pass a tax bill and President Trump trying to put additional pressure on representatives and senators by vetoing a short-term CR or full-year appropriations.” That’s the worst-case scenario — a president desperate for a legislative win using the threat of a government shutdown to pressure Congress on tax cuts. The end result could be a shuttered government.