  In this paper, we analyze the full evolution, from a few days prior to the
eruption to the initiation, and the final acceleration and propagation, of the
CME that occurred on 2008 April 26 using the unprecedented high cadence and
multi-wavelength observations by STEREO. There existed frequent filament
activities and EUV jets prior to the CME eruption for a few days. These
activities were probably caused by the magnetic reconnection in the lower
atmosphere driven by photospheric convergence motions, which were evident in
the sequence of magnetogram images from MDI (Michelson Doppler Imager) onboard
SOHO. The slow low-layer magnetic reconnection may be responsible for the
storage of magnetic free energy in the corona and the formation of a sigmoidal
core field or a flux rope leading to the eventual eruption. The occurrence of
EUV brightenings in the sigmoidal core field prior to the rise of the flux rope
implies that the eruption was triggered by the inner tether-cutting
reconnection, but not the external breakout reconnection. During the period of
impulsive acceleration, the time profile of the CME acceleration in the inner
corona is found to be consistent with the time profile of the reconnection
electric field inferred from the footpoint separation and the RHESSI 15-25 keV
HXR flux curve of the associated flare. The full evolution of this CME can be
described in four distinct phases: the build-up phase, initiation phase, main
acceleration phase, and propagation phase. The physical properties and the
transition between these phases are discussed, in an attempt to provide a
global picture of CME dynamic evolution.
