Casey, who retained his seat by 9.1 points and around 500,000 votes, spent around $7 million less, close to $14 million.
Some of Smith's spending included his primary run against a crowded field of Republican hopefuls last spring. Casey did not have a serious primary fight.
While Casey ended up winning handily on Nov. 6, in the final weeks of the campaign some public polls showed Smith having an outside chance of upsetting the first term senator.
From Oct. 18, Casey matched Smith's spending with each outlaying just over $3 million in the home stretch, according to Federal Election Commission reports from both campaigns.
For the entire cycle, Casey raised around $13 million while Smith raised close to $5.3 million.
By comparison, in 2010, Republican Pat Toomey raised $17 million and spent around $16 million and Democrat Joe Sestak raised around $8.5 million and spent $7.5 million, according to Opensecrets.org. However, there was around $30 million spent by outside groups on that race, which was considered one of the most high profile of that year.
Some numbers have been updated since first post.