What factors led to the religious revivals known as the Second Great Awakening?

The main factor that led to the Second Great Awakening was
the Enlightenment and the decrease in religious fervor that went along with it.  The
Second Great Awakening is seen as a response to or a backlash against those
developments.

During the time before the Second Great
Awakening, Enlightenment ideas such as Deism and Unitarianism had been gaining
popularity in the US.  These were ideas that generally had less emotion to them.  They
saw God as disinterested (Deism) or simply a kind and loving father (Unitarianism). 
Neither had an "old-time religion" feel to them that emphasized an emotional connection
to God or a deep fear/awe of him.

Historians argue that
this swing of the pendulum towards liberalism in religion led to a reversal.  The
pendulum swung back towards more traditional views of religion.  This reversal was the
Second Great Awakening.

In this way, the Enlightenment move
towards liberal, modern ideas is what sparked the Second Great
Awakening.