Is this a sentence fragment?
With more than sixty percent of the popular vote, incumbent Lyndon Baines Johnson defeating Republican Barry Goldwater, Sr., in the 1964 presidential election.
no yes
A sentence is a group of words that expresses a complete thought.
The band I'm in has been rehearsing daily because we have a concert in two weeks.
A sentence fragment is a group of words that does not express a complete thought.
Rehearsing daily because we have a concert in two weeks.
This fragment is missing a subject. It doesn't tell who is rehearsing.
The band I'm in.
This fragment is missing a verb. It doesn't tell what the band I'm in is doing.
Because we have a concert in two weeks.
This fragment is missing an independent clause. It doesn't tell what happened because of the concert.
This is a sentence fragment. It does not express a complete thought.
With more than sixty percent of the popular vote, incumbent Lyndon Baines Johnson defeating Republican Barry Goldwater, Sr., in the 1964 presidential election.
Here is one way to fix the sentence fragment:
With more than sixty percent of the popular vote, incumbent Lyndon Baines Johnson defeated Republican Barry Goldwater, Sr., in the 1964 presidential election.