Early in the evening, after the polls closed but long before the election results came in, Nate Cohn of the New York Times tweeted that the Mississippi Republican runoff between U.S. Senator Thad Cochran and state Senator Chris McDaniel "is close enough that it really will depend on the details of the margin and turnout in the big, outstanding base counties."

http://twitter.com/Nate_Cohn/status/481626086913372161

While Cochran, the six-term incumbent senator, eked out a win in a runoff election, turnout was a major concern among the two candidates, which influenced the spending of their exorbitantly financed campaigns. Indeed, while Cochran will now go on to defend his incumbency against Travis Childers (who won the Democratic primary in early June), one of the enduring legacies of this campaign may be on how the open partisan primary system influenced spending patterns.

Cochran, in a bid for a seventh term in office, hoped to ward off McDaniel, who is championed by the tea party. In the June primary, McDaniel led Cochran by approximately 1,400 votes. Without the majority required to advance, a runoff primary was set for June 24.

polling by approximately six percentage points going into Tuesday's runoff. Defying the polls, Cochran won with 50.9 percent to McDaniel's 49.1 percent, which equated to about 6,600 votes out of more than 372,000 that were cast.

Mississippi has an open partisan primary system. Whereas closed primary systems require voters to register with a party before voting in their primary elections, Mississippi allows its citizens to choose which party ballot they want to vote on, without declaring party membership.

However, in the runoff election, if voters cast their ballot in the Democratic primary, they are not allowed to vote in the Republican runoff, having already declared their party of choice. On Tuesday night, some calls to the election office addressed issues of people who had voted in the Democratic primary, but were attempting to vote in the high profile Republican runoff. The number of complaints though would not have influenced the outcome of the election.

Overall, Cochran’s win is heavily attributed to boosting voter turnout beyond the traditional Republican ranks. His campaign targeted black Democrats in the state who had not voted in the primary election, and ultimately boosted his numbers in counties he had not won in the original primary. Turnout across the state increased by about 16 percent over the original primary.

Clearly, the open primary had implications on the results of Tuesday’s runoff as Cochran was able to broaden the voting demographics his campaign targeted. In order to target turnout, Cochran and McDaniel both shifted their campaign spending strategies as well.

most expensive in the state’s history. However, as Derek Willis of the New York Times reports, much of the efforts were directed to ensure high voter turnout beyond the traditional media venues.

In Willis’ piece, he notes that in many primaries, broadcast mediums, such as radio and television, make up roughly 93 percent of spending, whereas in Mississippi, only 74 percent was spent on broadcast costs. Instead, spending tended to focus on direct mail and online efforts which was seen as more effective in getting people to the polls.

More research is currently being done to analyze what the best methods for turnout can be.

For example, one study conducted by David Nickerson of Notre Dame acknowledged that voter turnout can increase with telephone calls, but professional callers do not aid the effort and only personal ones have a positive impact. Other political scientists have considered the possibility of incentivizing voting to increase turnout.

Meanwhile, another study conducted found that increasing information in advertisement, and thus creating informed voters, created higher turnout in particular populations. Some of these studies undoubtedly influenced the method of spending in Mississippi over the past several weeks.

Mississippi’s election will no doubt be the subject of its own future study on analyzing the different methods of campaign spending, as well as their impact in the coming months. Attracting a wider percentage of the state’s voters is certainly an encouraging step, but how to impact that vote also provides interesting challenges.

In the meantime, Cochran hopes to gear up for a fight against Childers, although many in Mississippi believe the biggest challenge for Cochran was in the primary. The last Democratic senator in Mississippi left office in 1989.