Some candidates on Tuesday may get a boost — from the ballot itself.

Appearing first on a ballot can be worth as much as 2.3 percentage points more votes, enough to swing a close race.

That number comes from research by Jonathan Koppell and Jennifer Steen, political science professors at Yale University and Arizona State University, respectively.

They looked at the 1998 Democratic primary in New York to test their hypothesis that ballot order mattered.

Because New York rotates the order in which candidates are listed in every precinct, Koppell and Steen were able to test how well the candidates did who were listed first. They found the advantage was from 1.6 to 2.3 percentage points.

"People economize," Steen told Congress.org. "Political scientists have borrowed this concept from economists and political psychologists. The theory is that one time- or labor-saving device is to make an easy decision, and when you're presented with a list of choices in a written format, you'll pick the first one that is acceptable to you."

She said that the effect is most likely in "low-information elections," in which people are not familiar with the candidates, such as local or nonpartisan offices. She does not think it has as much effect on high-profile races for Congress, except in some tight races.

Below, we took a look at how some states with competitive Senate races determine a candidate's position on the ballot.

1. Florida (Projection: Leans Republican)

In Florida, the top slot on the ballot goes to the candidate whose party controls the governor's office.

In theory, that would benefit Charlie Crist, the current governor and a candidate for Senate.

But Crist dropped out of the Republican party when it appeared he would lose the Senate primary to Speaker of the House Marco Rubio, so it is Rubio's name, not Crist's, at the top.

Crist is now running as an independent, and like in many states, independents are listed below major party candidates.

In addition, independents are listed in the order in which they filed their candidacy papers, so Crist—who has been running second in the polls—is actually listed ninth on the ballot.

2. West Virginia (Projection: Tossup)

West Virginia's system of determining ballot order refers back to the previous presidential election.

Republican presidential candidate John McCain won the state in 2008, so this year's Republican Senate candidate, John Raese, appears first on the ballot.

Barack Obama garnered the second-most votes in 2008, so Gov. Joe Manchin II (D) is listed second on the ballot in every county in West Virginia.

That might mean a slight advantage for Raese, and if the effect of ballot placement approaches two percent of the vote, as it did in Steen's study of the New York Democratic primary, it could make a big difference in this tight race.

3. Illinois (Projection: Tossup)

Illinois determines its candidate order by a random lottery in 110 different constituencies (102 counties and eight municipal board of elections commissioners), according to Ken Menzel, the state Board of Elections' legal counsel.

What that means for the two candidates running neck-and-neck to fill President Barack Obama's old seat—Democrat Alexi Giannoulias and Republican Mark Kirk—is that ballot order is unlikely to have much of an impact in Illinois as long as they each appear first about 50 percent of the time.

On another note: Rich Whitney, a candidate for governor, has reason to gripe about the ballot. He was placed in the correct slot, but his name is misspelled in some precincts—his name appears as "Rich Whitey."

4. California (Projection: Tossup)

California's unique system of determining ballot placement centers on an alphabet drawing.

The Secretary of State's office holds a lottery in which it pulls every letter of the alphabet to create a new alphabetical order that applies to every position on the ballot.

For Senate, the new alphabetical order is the same as the old one: Democratic incumbent Barbara Boxer will appear above challenger Carly Fiorina, because the letter "B" was drawn ninth and "F" went 14th.

The state rotates candidate order across assembly districts all over California, though, so Boxer and Fiorina will alternate at the top of the ballot irrespective of the results of the alphabet drawing.

5. Colorado (Projection: Tossup)

Colorado holds a lottery for Senate balloting, like many states do, that involves three categories: major parties, minor parties and independents.

All major-party candidates will be listed above all others, and on down the line.

In this year's lottery, the Republican Party was drawn first and the Democratic Party second, so Ken Buck will get the nod at the top of the ballot ahead of Michael Bennet in every county in Colorado.

As in West Virginia, this race could be decided by just a few percentage points.

6. Alaska (Projection: Leans Republican)

The Last Frontier State is a little different than most others in this election because of the presence of a viable write-in candidate, Republican Lisa Murkowski.

Her name will not appear on the ballot.

The names of those that do appear—Joe Miller (R), Scott McAdams (D), and three others—will be rotated in every county in Alaska, nullifying the top-of-the-ballot advantage for any one candidate.

The write-in slot on the ballot is below that of all other candidates, as is customary.

Kaitlin Kovach contributed to this story.

Gabe Starosta writes for Roll Call.

Correction: An earlier version of this post misstated the exact nature of California's ballot system.

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