House Republicans have proven themselves an unruly bunch over the past two years -- first electing Johnson after taking the unprecedented step of ousting his predecessor Kevin McCarthy in the middle of his term -- and will have a scant 219-215 majority when their new members are sworn in on Friday.
Trump sought to clear the way for a smooth ride after he endorsed Johnson on Monday following weeks of uncertainty.
"Speaker Mike Johnson is a good, hard working, religious man. He will do the right thing, and we will continue to WIN," Trump posted online.
Johnson this week has tried to project confidence. "We have the smallest margin in U.S. history. We’ll have a margin of probably two votes ... but I think we'll get it done," the speaker told Fox News on Thursday about his chances. "We cannot afford any palace drama here."
Maverick Republican Representative Thomas Massie, a regular thorn in the saddle for his party's leaders, has vowed to vote against Johnson. Several other party members have been coy about whether they would back him.
More than one vote against Johnson, or multiple Republican abstentions in the form of "present" votes, would be enough to block Johnson's re-election if all Democrats vote for their leader, Hakeem Jeffries, as they are expected to do.
Whoever secures the speakership -- a role that is second in line to the presidency after the vice president -- will have a big job ahead. In addition to passing Trump's sweeping legislative agenda, which includes tax cuts and immigration changes, Congress will need to address the nation's debt ceiling later this year.
With the federal government already more than $36 trillion in debt, many congressional Republicans are expected to demand significant spending cuts.
Republicans will also be sworn in to their new 53-47 Senate majority on Friday, and are expected to elect Senator John Thune as their new leader, succeeding long-serving Senator Mitch McConnell, who is stepping aside from leadership but remaining in office.
'EMPEROR HAS NO CLOTHES'
Massie argued on social media this week against Johnson's leadership abilities within the Republican conference.
"He won’t tell the President what is achievable and what is not achievable in the House, and he lacks the situational awareness himself to know what can pass and what cannot," Massie said, "The emperor has no clothes and the entire conference knows it but few will say it. The general public knows it too."
Johnson angered some conservatives by repeatedly turning to Democrats to provide the votes to pass critical legislation, like bills to keep government agencies operating. He also faced a last-minute challenge late last month when Trump told House Republicans to scrap a government funding deal, demanding it also raise the nation's debt ceiling.
A revised version of that bill -- not including Trump's debt-ceiling demand -- passed the House only a few hours before the government would have shut down and received more support from Democrats than Republicans.
Other Republicans -- trying to claim the mantle of defending Trump's second-term agenda -- have made demands in exchange for their support.
Republican Representative Victoria Spartz this week released a wish-list of fiscal structural restraints in the year ahead, opening the door to Johnson winning her over.
So far, no other Republican has publicly hinted at challenging Johnson for the role.
One other element working in Johnson's favor for staying on as speaker is the calendar.
Congress is scheduled to meet on Jan. 6 to certify Trump's presidential election victory, a function it will be unable to perform without a speaker.
Johnson has also looked to make his path for the next two years easier, by changing a rule agreed to by McCarthy that allowed any one member of the House to call for the speaker's ouster through what is known as a "motion to vacate." Johnson's proposed rules would require nine members of the majority to agree before forcing the type of vote that led to McCarthy's ouster.
