Trump writes on his platform Truth Social that Johnson has his full support and that he is a "good, hardworking religious man" who will make the right decisions.
Johnson seemed to be on shaky ground earlier in December in connection with a battle in Congress over a temporary budget agreement to avoid a government shutdown.
The battle revealed the limited influence of the Speaker over the party group, which showed clear cracks in its support for him.
Johnson's first two attempts to reach an agreement fell through after Trump, who takes office as president on January 20, intervened and made demands.
It wasn't until Trump dropped his demands that an agreement was reached.
