@hszmv's excellent asswer already alludes to this - there is also another major factor, to whit, the guys with big sticks. AKA, the military.

Obviously, how the military feels about things has a very large effect on success of any major national transformation.

• If the majority of the military opposes your bid for power, no matter how "legal"/"democratic", they will get rid of you.

  The most obvious and recent case in point is Egypt; where Mursi tried to do something similar (gain power democratically, try to re-write the laws to become less democratic theocracy - this is bumper sticker level, without nuance). The military took a dim view of that, resulting in Mursi ending in jail and Al-Sisi being in power.

• Whereas, if the military/law enforcement at large supports your bid for power, they will support you, not only against your own people; but even against dissenting parts of the military.

  Most relevant recent example: Turkey, and the abortive coup attempt against Edrogan (this is especially notable due to the fact that, since Ataturk, the military was by design the guarantor of secularism in Turkey - the last time in 1997).

• More pertinent to USA, the army is typically very ideologically supportive to constitution (see the oaths taken by every officer); and has a history of NOT being interested in establishing dictatorships, for example see Butler's example in 1930s.

  I will support and defend the Constitution of the United States against all enemies, foreign and domestic...

@hszmv's excellent answer already alludes to this - there is also another major factor, to whit, the guys with big sticks. AKA, the military.

Obviously, how the military feels about things has a very large effect on success of any major national transformation.

• If the majority of the military opposes your bid for power, no matter how "legal"/"democratic", they will get rid of you.

  The most obvious and recent case in point is Egypt; where Mursi tried to do something similar (gain power democratically, try to re-write the laws to become less democratic theocracy - this is bumper sticker level, without nuance). The military took a dim view of that, resulting in Mursi ending in jail and Al-Sisi being in power.

• Whereas, if the military/law enforcement at large supports your bid for power, they will support you, not only against your own people; but even against dissenting parts of the military.

  Most relevant recent example: Turkey, and the abortive coup attempt against Erdoğan (this is especially notable due to the fact that, since Ataturk, the military was by design the guarantor of secularism in Turkey - the last time in 1997).

• More pertinent to USA, the army is typically very ideologically supportive to constitution (see the oaths taken by every officer); and has a history of NOT being interested in establishing dictatorships, for example see Butler's example in 1930s.

  I will support and defend the Constitution of the United States against all enemies, foreign and domestic...