Defunding Obama's immigration agenda
Whether there is a shutdown is up to Obama. If he wants to shut down the government to coerce funding of his lawless approach to immigration Democrats will pay a heavy price. His immigration policy is already unpopular and this would only make it more so.
President Obama is believed to be preparing to take executive action on immigration, and Republicans are considering removing funding to effectively block the order, possibly prompting a spending stalemate just before November elections.