To begin the process of fundamentally changing the Presidential term of office from 4 to 6 years - and one term only.

The first term in office for the President has possibly two years of worth; the first few months are spent learning the ropes, and the last two are comsumed with campaigning for a possible second term.
By giving the POTUS one 6 year term, we get a President - not a campaigner; the focus will be on the job and not poll numbers. We also have an individual that will be in office long enough to feel the effect of his or her decisions.
A single six year term keeps the President focused and accountable!