With the March 18 primary approaching for the Illinois gubernatorial race, 4 Republicans are vying for the favor of voters and a large swath of undecided voters may make the difference.

Illinois is currently dealing with a downgraded credit rating and a public pensions crisis. Hovering between 8 and 9 percent, unemployment is still above the national average.

With big names dropping out or declining to run, Democratic governor Pat Quinn is running against only token opposition in his primary. With approval ratings consistently in the 30s, Quinn is considered one of the more vulnerable governors running for re-election in 2014.

On the Republican side, the battle is being fought between Chicago businessman Bruce Rauner, State Senators Kirk Dillard and Bill Brady, and state Treasurer Dan Rutherford.

A former state senator, Rutherford is being sued by a former staffer over allegations of sexual harassment. The staffer also claims that Rutherford pressured him to do political work on state time. Rutherford has denied the charges and vowed to remain in the race. The only candidate in the primary who has won a statewide election, polls have shown him steadily losing support.

Kirk Dillard has been in the state senate since first winning office in 1994 and has spent much of the 2014 campaign defending himself -- particularly from colleague Bill Brady -- over an old campaign ad praising Barack Obama.

The ad featuring Dillard ran during the 2008 presidential election where Dillard discussed Obama's time in the state senate, saying the future president was "successful in a bipartisan way." He also said that Obama had "negotiation skills and an ability to understand both sides" that "would serve the country well."

Dillard has responded to this criticism by saying it was "just an Internet thing" and called Obama to say the ad ought to be pulled because "you know I'm for John McCain."

Bill Brady was the Republican gubernatorial nominee in 2010 and lost to Quinn by less than one full percentage point. Brady won all Illinois counties except the most populous, Cook, as well as St. Clair, Jackson, and Alexander in the south. Hoping to expand his voter base from 4 years ago, from which he emerged in a seven candidate primary field, Brady's poll numbers have stagnated.

Leading most polls is Chicago businessman Bruce Rauner. A first-time candidate, Rauner made millions in venture capitalism and has dominated Illinois airwaves with advertising. His $6 million spent so far is a record for an Illinois gubernatorial candidate with much of it coming from his own pockets.

Running as an outsider against

entrenched corruption, for term limits, for pension reform, and ending teacher tenure, Rauner has also had to address questions about his previous financial dealings and political support. Although he has since been donating to Republicans, prior to 2002 Rauner and his wife regularly donated to Democratic candidates, which included Rahm Emanuel, Dick Durbin, and President Obama's 2004 U.S. Senate campaign.

In a recent interview with the Chicago Sun-Times, Emanuel said Rauner is a friend and that they only met after Emanuel left the Clinton administration, but only vaguely mentioned that Rauner helped him make a "transaction."

At the latest debate, Rauner defended himself saying that although he does not agree with Emanuel on much:

"He wants a better business climate in Chicago, he needs that, he needs major pension reform, he wants school choice so I'll find common ground and I'll work with him to solve problems together."

While Rauner has held a sizable lead in the race, his lead is dwindling as voting approaches. The Real Clear Politics poll average shows Rauner's lead at almost 20 points. However, the latest WGN/Chicago Tribune poll shows Rauner dropping from over 40 down to 38 while Dillard is up to 23 and Brady treads at 18. Despite Rauner's once big lead, there were always many voters left undecided. As Rauner's lead has shrunk, more are moving toward the Dillard camp.

Compared to any potential Republican general election candidate, Governor Quinn looks in good shape for such a vulnerable incumbent. A February poll from Public Policy Polling showed that while Rutherford was the only candidate Quinn led, Dillard had the highest advantage of any potential rival and that was by less than 4 percent, 40.2 to 36.5. Regardless of the poll numbers, there are many undecided voters for both the Republican primary and general election.

Photo Credit: Charles Rex / AP