The At-Large election has some advantages. It is one big electoral event that is for all the nation, the only one aside from the presidential election. It usually gets high participation. Since it is one national election it is easier to organize a debate and have the focus on that. Since it is addressed to all voters it is worth doing a public campaign for a candidate. For candidates it is a chance to come in contact with people in all the nation. At-Large offers a different way for someone to enter the Senate while districts are more identical regional Senate election. Someone who is not popular or not well-known or who is less mainstream but backed by a big party can be elected in At-Large.
The at-large elections are, on the other hand, increasingly rarely competitive. The two most recent elections have featured six candidates running for five seats, with little doubt as to whom the five elected would be. This is often due to the fact that no major party has ever won more than two seats at a general at-large election, or has ever been foolish enough to consciously risk splitting their candidates' vote three ways.
To be fair, I don't think many of the 130 voters actively followed the campaign or paid attention to the debates. Partisanship is far and away the best predictor, time and time again, of how an Atlasian will vote. The supporters you have won with your vigorous campaigning just haven't been enough to match the parties' vigorous GOTV efforts of their registered members, nor is your ideological niche large enough to siphon off enough votes from the center-right or center-left.
