3 ideas
A voter refused today is lost right away and resents it, while a voter given a promise stays loyal until the promise comes due. Many of those promises will never come due, because circumstances change or the favor is never asked for. So the candidate should agree readily and handle the cost of failing to deliver later, since a vague yes loses fewer votes than an honest no.
During a campaign, 'friend' is stretched to cover anyone who shows goodwill: family, household, neighbors, freedmen, and then members of guilds and districts. The candidate recruits leaders who each command a network, so one personal tie reaches many votes. Support is built by tying people to you through favors already done, favors hoped for, and personal attachment. Each tie is used according to its type.
Remembering names, flattering people, being easy to reach, and keeping a crowd around you are campaign tools, not personal virtues. Voters judge how much a candidate will care about them by how personally he seems to know them, so a practiced display of attention creates a sense of closeness. A visible entourage also signals momentum and draws in more supporters.