There can be several right answers for this blank. The following are a couple words that can correctly fill the space.
1) John McCain was a Republican at the time of the 2008 election- He was the Republican party's nominee for President with his running mate being Sarah Palin.
2) John McCain was a Senator at the time of the 2008 election- He was a Senator representing the state of Arizona in the US Congress before starting his run for the presidency.
