Final answer:
The phrase 'could begin a lifetime of such civic engagement' best helps the reader determine the meaning of habitual as it implies that voting is an activity that becomes a regular behavior over time.
Step-by-step explanation:
Selecting the phrase that best helps readers determine the meaning of the word habitual in the given sentence, we should consider the context that surrounds the term. The phrases provided all offer insights into different aspects associated with voting behavior, but not all are directly related to the term 'habitual'. The phrase that best helps understand 'habitual' within the context of voter turnout is 'could begin a lifetime of such civic engagement' because it suggests that the act of voting becomes a repeated behavior over time, hence habitual.
When examining the determinants of voter turnout, we see that institutional factors and individual-level characteristics, such as age and civic engagement, have a significant impact. For instance, older voters tend to have higher turnout rates, partly because voting becomes more of a habit to them as they age. Additionally, ease of voting - through measures like all-mail voting, extended polling hours, or even moving elections to weekends - can influence the rates of voter participation.