There’s zero possibility this goes most of the year. I don’t think it goes most of the month. Trump has no leverage on Pelosi at all, not even a feather. McConnell knows that the Republicans will weather the lion’s share of the blame for this, and if people start filing taxes with no returns, that’s the ballgame for 2020, 2022, and probably 2024.
The most likely outcome is that McConnell passes whatever the House wants, with maybe a fig leaf (if Pelosi even gives them that), and he pulls enough Republicans in the Senate together to pass it over Trump’s objections. This ends very badly for Trump, badly for the Republicans, as literally everyone could have predicted.
This is going to be the lesson that Republicans get to learn over and over in the first half of this year; they’ve been in charge of Congress for years, and put all of their back bench dumbshits in charge of everything, and a lot of them have just been thinking that’s how things are. They’re weak, they’re soft, and they’re lazy, and they’re going up against serious, competent professionals – and that’s before you even get to Trump himself, who is weak, undisciplined, lazy and incapable of keeping his mouth shut. They’re not at all used to professional, competent opposition, and the shutdown is just the very first taste of how bad things are going to be for them, all year long.