Iraq War veteran Joni Ernst emerged as the Republican frontrunner this week in the race to replace retiring Sen. Tom Harkin (D., Iowa).

Ernst, who served as a company commander in Iraq from 2003 to 2004 and is a mother of three, gained a slight advantage over the other four candidates for the GOP Senate nomination in a Suffolk University poll.

Ernst has 25 percent support among likely primary goers, followed closely by wealthy businessman Mark Jacobs with 23 percent. The other three candidates received less than 10 percent, while 40 percent are still undecided for the June 3 primary.

Ernst has portrayed herself as a candidate who could unite grassroots conservatives in Iowa with the GOP establishment. She has secured key endorsements from both of those Republican factions, including former presidential candidate Mitt Romney and former Alaska Gov. Sarah Palin. She would also be the first woman elected in Iowa to either the governorship or Congress.

One thing that separates Ernst from the pack is her focus on national defense, which has elicited comparisons to other defense hawks such as Sen. Kelly Ayotte (R., N.H.).

Ernst told the Washington Free Beacon in an interview that a strong military "is a must in order to remain a world player." Defense budget cuts known as sequestration could drain almost $1 trillion from the Pentagon in the next decade if they remain in place.

"It’s especially important as we look at Syria, Iran, what has happened in Egypt, and North Korea, that we have a strong stamp whether it’s foreign policy or national defense," she said.

Ernst participated in an agricultural exchange program in Ukraine while attending Iowa State University, before the fall of the Soviet Union. Her experience living on a small farm in Ukraine convinced her to serve in the military, she said.

"It was very different from the freedom we enjoy in the U.S.," she said. "That was the reason that when I got back from the exchange program I asked, ‘How can I serve my country?’ And that was joining Army ROTC and going on to join the armed forces. That has made a great impact on my life."

Ernst said her candidacy presents a "clear contrast" with Jacobs in the GOP primary and Bruce Braley, the sole Democratic candidate and a four-term Iowa congressman.

Jacobs, a former Goldman Sachs employee and energy executive, has been criticized by some Republican observers for donating to Democrats Jon Corzine and Arlen Specter. He also expressed support in 2007 for a "market-based cap and trade system" as CEO of Texas-based Reliant Energy. Republicans typically oppose a cap and trade system as a regulatory scheme that would raise energy prices.

Jacobs’ campaign did not respond to a request for comment. Spokeswoman Alissa Ohl told the Weekly Standard in February that while Jacobs "never personally support[ed] a cap and trade alternative," he was "forced to decide if he wanted to ‘be at the table, or on the table’" since Reliant owned coal-fired power plants in Specter’s home state of Pennsylvania.

Braley, a trial lawyer, faces his own problems in the general election. He told a group of lawyers at a January fundraiser that he would be their "voice" for fighting tort reform in the Senate, adding that fellow Sen. Chuck Grassley (R., Iowa) was "a farmer from Iowa who never went to law school." Many viewed his comments as elitist in a farming-heavy state like Iowa.

Braley later apologized for the comments and said he "was simply pointing out that we have different life experiences." Lawyers and law firms have already donated more than $1 million to his campaign this cycle, according to the Center for Responsive Politics.

Braley maintains a lead in the polls and fundraising as he awaits his GOP opponent. His campaign has largely stayed out of the primary but has claimed that "Mark Jacobs fights for Wall Street."

Timothy Hagle, political science professor at the University of Iowa, said in an interview that Ernst would potentially be a stronger competitor against Braley than Jacobs. If no GOP candidate wins 35 percent of the vote in the primary, a nominee will be selected at a June 14 convention.

"If Jacob gets it, the standard [Democratic] attacks—many of which were used against Romney, the big CEOs, big corporations—could be problematic," Hagle said. "It’s something he would have to address."

For Ernst, who is still in session as an Iowa state senator, her campaign has settled on a theme going forward. Her first ad garnered national headlines for touting her background as someone who "grew up castrating hogs on an Iowa farm."

"I’m going to work for all Iowans, not just trial attorneys and not for big energy executives," she said.