(CNN) The President's tweet Sunday caught Capitol Hill Republicans completely off-guard -- and set off a scramble to figure out what he actually meant.

Quietly, this year's appropriations process has been one of the few bipartisan success stories of recent years -- and President Donald Trump actually deserves a good bit of credit for it due to his veto threats after signing the omnibus spending bill in March.

Bottom line: A shutdown fight is coming. Period. The President and his top advisers want it -- and view it to be politically beneficial when it comes to immigration and the wall, according to multiple aides involved in spending discussions.

The goal of GOP leaders has been to push it until after the election. They were sure they were in good shape after the meeting last week. Sunday's tweets scrambled that, but by late afternoon, senior aides felt things were still OK.

"Just letting off some steam," one said. "At our expense, per usual."

What drove the tweet

The President's staff has been fired up about provisions included in the House Homeland Security Department spending measure, approved in committee last week. That was part of the reason, sources say.

Another is that there was a segment on Fox News' "Fox and Friends" on Sunday morning shortly before the tweet.

Also about 20 minutes before the tweet: CNN's "Inside Politics" panel -- which included the author of this report -- laid out why GOP leaders felt good about where things stood. That discussion included the all-important caveat that a presidential tweet could blow everything up.

Spending state of play

The Senate will have passed seven bills by the end of this week. The House has already moved all 12 through committee.

In the Senate, despite the constant attacks and tension between the Republican and Democratic leader, if you listen closely, they both take pains to compliment one another -- and Sens. Richard Shelby and Patrick Leahy, the top Republican and Democrat on the Appropriations Committee -- about how this process is proceeding.

The tentative goal at the moment is to reconcile nine of the 12 appropriations bills and send them to the President. The remaining three will have to be addressed by a continuing resolution before October.

The idea: That is a significantly smaller continuing resolution compared to those in the past. Getting nine appropriations bills signed into law is a big deal. Again, there is a long way to go before reaching that goal, but those two data points are, based on congressional GOP leaders plans, designed to convince the President to avoid the shutdown.

The wall: One of the bills that won't be reconciled is the Homeland Security measure, which is the vehicle for wall funding. The idea is to push the fight until after the election. Republicans already secured $1.6 billion for the process to begin. The fight for more funds to bring it closer to the $25 billion coveted by the President, will come at the end of the year.

The meeting: The above strategy is exactly what Speaker Paul Ryan and Senate Majority Leader Mitch McConnell laid out in their private meeting with the President last week, according to multiple sources. The President was amenable to the strategy -- and particular the point made by McConnell about a spending fight stepping all over the likely confirmation of Brett Kavanaugh, the Supreme Court nominee that would represent a huge win for the White House and Capitol Hill Republicans.

To make this perfectly clear, both lawmakers left the White House convinced the President was on board.

The irony here is that the President is actually the reason the appropriations process is, to some degree, actually working. His threats as he signed that $1.3 trillion omnibus were taken dead seriously -- by both parties. It has remained a driving influence in keeping the Senate talks bipartisan -- and fruitful, aides on both sides of the aisle tell me. In other words: The President is responsible for the process working for the first time in years. That's a big deal. Now the President is threatening to short-circuit that process.

One wild card to consider: Time. The Senate is in session almost all of August and will process its bills. The House is gone until September 4 and will fall behind. A couple of weeks to process three or so appropriations conference reports is not a ton of time for such legislation.

A second wild card to consider: Office of Management and Budget Director Mick Mulvaney. He's made clear in meetings he thinks spending cuts should be a priority in these spending bills -- something that would undercut the bipartisan deal made earlier this year, and also the bipartisanship driving the Hill negotiations up to this point. GOP leaders have made clear it's a strategy that won't play in this round of spending talks, but keep an eye on it -- not unlike the wall, it's likely to be an area the White House puts its foot down on in future negotiations.