Lee Smith is number 3 on the all time saves list, which is his strongest argument for the Hall. And he was a closer in the old sense of the word, he'd close out games pitching 2 or 3 innings, if needed.
He was an intimidating guy out on the mound. 6'5" and 220, maybe not as scary looking as Jon Rauch but a much better pitcher. He played on 7 All-Star teams, won 3 reliever of the year awards and came in second in the 1991 Cy Young voting.
Smith played for 8 different teams, including a season with the Expos, to finish out his career.
Right now there are only 5 relief pitchers in the Hall: Goose Gossage, Hoyt Wilhelm, Rollie Fingers, Bruce Sutter and Dennis Eckersley. Smith might not be quite as good as those 5 but he's close.
This is his 13th time on the ballot. Last year he was on 29.9%% of the ballots, which was his lowest score. Before that he was running between 40 and 50% the last few years. He was hurt by the number of very good players that came on the ballot.