President Trump reminded Republicans on Thursday how easily he could explode his party’s carefully crafted messaging strategy, signaling how difficult it will be to stay unified in the face of Democratic attacks in a challenging midterm election environment.

The House ultimately approved a short-term spending package in an evening vote after Republicans fell in line. The legislation advanced to the Senate, where it faced an uncertain fate because of opposition from both parties; passage requires a supermajority of 60 votes and Democrats are vowing to filibuster.

But Trump nearly upended the GOP's whole strategy. Republicans in Congress were set to blame Democrats for risking a government shutdown over a disagreement on immigration policy. Then the president, in an early morning tweet, voiced unexpected opposition to the bill, putting Republicans on defense just hours before the planned House vote.

The confusion wouldn’t clear for three hours — until House Speaker Paul Ryan, R-Wis., said that Trump reaffirmed his support for the legislation in a telephone conversation 90 minutes earlier. The episode illustrated the challenges ahead for Republicans as they seek to stay on message in the upcoming congressional campaigns.

“If you don’t like his decision today, just wait till tomorrow,” Rep. Mike Simpson, R-Idaho, a 20-year House veteran, told the Washington Examiner, chuckling as he took a jab at Trump.

“Obviously, it makes it more difficult,” Simpson added, when asked if the president’s communication style posed challenges for Republicans in upcoming campaigns. “It’s like [Senate Majority Leader] Mitch McConnell [R-Ky.] said yesterday: 'When we find out what he’s for, then we’ll know where we’re headed.'”

Unable to reach a long-term spending deal before midnight Friday, Republican leaders drafted a 28-day continuing resolution to keep the government operating at current funding levels to allow more time for negotiations.

Democrats generally oppose the bill because it does not include deportation relief for the “Dreamers,” illegal immigrants brought to the U.S. as young children who participated in the Deferred Action for Childhood Arrivals program. To force their hand, the Republicans paired the spending bill with a six-year reauthorization of the Children’s Health Insurance Program. CHIP provides healthcare to disadvantaged children and is a major Democratic priority.

GOP leaders were still struggling to secure enough votes from rank-and-file Republicans Thursday morning, ahead of the evening vote, when Trump tweeted: “CHIP should be part of a long term solution, not a 30 Day, or short term, extension!” The missive contradicted a statement in support of the bill issued by the White House the previous evening.

The president’s tweet fueled Democratic resistance to the CR, especially in the Senate; it somewhat mirrored Democratic talking points that Republicans shouldn’t leverage CHIP to keep the lights on in Washington. The tweet also encouraged resistant Republicans in the House Freedom Caucus, the party’s insurgent wing, to withhold their support, although most of them eventually voted in favor after securing minor concessions.

Some hours after the tweet, Marc Short, Trump’s chief liaison to Capitol Hill, suggested that the Republican-run Congress broadly would be responsible for any government shutdown, rather than blaming the minority Democrats specifically for obstructing a bipartisan agreement. “What’s missing in this conversation is the complete dysfunction of Congress,” he said, according to Politico.

Trump tried to steer public discussion back to tax reform and the booming economy Thursday afternoon during a well-received speech in Pennsylvania. "If we keep it up like this, we're going to win a lot of elections," Trump said. "'It's the economy, stupid.' You ever hear that one?"

This isn’t the first time Trump has pushed his party off message, without warning, via tweet or in an interview. It happened regularly last year, particularly during the since-collapsed effort to repeal and replace Obamacare and, more recently, this month when an errant tweet nearly derailed reauthorization of government spying powers considered crucial to national security.

But with less than 10 months to go until the midterms and the Republicans fighting an uphill battle, the consequences are potentially dire. The GOP is defending congressional majorities amid Trump’s 40 percent job approval rating and a generic ballot showing voters prefer Democrats be in charge on Capitol Hill.

That’s why Republicans are working so hard to keep the focus on tax reform.

The party believes its chances in 2018 are directly tied to voter support for the Tax Cuts and Jobs Act that Trump signed last month. Since its enactment, corporations have been announcing bonuses and wage hikes for workers, plus plans to invest in new facilities and hiring, and crediting tax reform for the moves. This is where Republicans want to keep the spotlight.

A government shutdown would be a distraction, with no guarantee that voters would blame Democrats for the impasse. Even if Democrats suffer, a shutdown would still grab headlines and get in the way of touting tax reform. Republicans concede they can ill afford more episodes like this in the months ahead.

"I see no scenario where we keep the House if the tax bill is unpopular,” a Republican strategist said. "It all starts and ends with the tax bill. When we screwed up Obamacare [repeal] it just made this much more important."