Dem
47
GOP
53
Donald Trump has two priorities for early in his second term: immigration (bad) and cutting taxes (good). Some Republicans in Congress want one giant bill with everything and some want separate bills. It could matter. Longer bills are harder to write and shepherd through Congress, especially if the Republicans have only a 217-215 or 217-214 margin for the first 3 months. A bigger bill has a larger attack surface. But two bills requires two big campaigns to get them through and the folks who opposed the first one may double down to kill the second one.
One argument for two bills is that a tax bill is entirely about the budget and can be done using the budget reconciliation process. Defending the border has some budget aspects—for example, appropriating more money for the Customs and Border Patrol—but other issues, like creating new border-related crimes or increasing penalties for existing crimes, probably would be flagged by the Senate parliamentarian, slowing down the process. First getting a clean tax bill through and then fighting about the border might make parliamentary sense. The only problem there is that the base cares not a whit about slashing Elon Musk's tax bill. If Trump gets a tax bill through quickly and the border bill then gets tied up in Congress, that sends the base the (correct) message that Trump's real priority is cutting taxes for billionaires.
But even if Trump takes the "easy" path of tax bill first, then the border, some deficit hawks may balk at increasing the deficit and may demand contentious cuts in popular programs that other Republicans may be afraid to cut. Also, incoming Senate Majority Leader John Thune (R-SD) has said that his first priority is the border, which may put the tough bill first and may mean not achieving any quick wins, especially if the House has to wait for all the special elections in April to get back to a 220-215 House.
One possibility is to revive the Lankford bill that Trump killed earlier this year. The problem with that is now the Democrats may not want to give Trump an early win and could filibuster it in the Senate unless they get some goodies that are anathema to Trump—for example, a path to citizenship for the Dreamers.
A huge factor in all this is Donald Trump's strategy. The trouble here is that Trump does not have a legislative strategy. He has a wish list. They are not the same. An additional complication is that there are many, many lobbyists from big corporations who: (1) want the tax bill first and (2) want most of the cuts to go to big corporations. That may be in conflict with the wishes of billionaires like Elon Musk who might prefer cutting the top tax rate for individuals as the highest priority. In short, the sausage(s) haven't been made yet and the process will surely be messy and probably slower than Trump would like. It may also produce less sausage than he's wanting. (V)