House Republicans stood strongly with President Trump giving him leverage to get a compromise 5 billion of his 25 billion dollars for a border wall. Senate Democrats and irrelevant until January House democrats oppose the border security measure. While President Trump lost nearly 40 House seats, he gained 2 Senate seats. This is similar to Reagan’s midterm where he held on to a 53 to 47 majority but lost his working majority in the House of Representatives.
Pelosi staked out an extreme and illogical stand against any physical border security measure. This fact necessitated that the President try to gain whatever leverage he has now. Accepting a short term measure is illogical. It is better to take a full year spending deal than just set up another fight where Republicans are weaker in February. Passage by the House of an appropriation bill that funded border security and included help for disaster relief which the Senate neglected, places the burden of any shutdown on Senate Democrats who say they believe one is irresponsible. If it is so irresponsible to have a shutdown, than why not pass the House bill? There is no logical reason to filibuster over a few billion dollars except to place denying Trump a victory over everything else.
While the President was willing to own a partial shutdown by a veto, it turned out he did not have to. It is all on the Senate now.