In July 2013, Ernst announced that she would seek the Senate seat held by retiring Democratic Senator Tom Harkin.
Iowa Lieutenant Governor Kim Reynolds endorsed her in October 2013.
She was also endorsed by 23 current and former state legislators.
In March 2014 former Massachusetts Governor Mitt Romney and former Alaska Governor Sarah Palin endorsed Ernst.
In May 2014, the U.S. Chamber of Commerce endorsed her.

Ernst received widespread attention for a campaign advertisement she released in March 2014 in which she made a tongue-in-cheek comparison between her experience castrating pigs and her ability to cut "pork" in Congress.
Many found the ad humorous and it was spoofed by late-night comedians, including Jimmy Fallon and Stephen Colbert.
Before the ad aired, Ernst had struggled to raise money, and two polls of the Republican primary taken in February 2014 had shown her in second place, several points behind Mark Jacobs.
After it aired, a Suffolk University poll in early April showed her with a narrow lead and a Loras College poll showed her essentially tied with Jacobs.
By May, she was being described in the media as the "strong front-runner".

In a May 9, 2014, Des Moines Register interview, Ernst said she was "extremely offended" by comments Jacobs made characterizing her as AWOL due to missing over 100 votes in the legislative session ending April 7, 2014.
Ernst said, "If [Jacobs] had any sort of service like I have, he would've understood what AWOL means.
I have not been AWOL, I will never be AWOL."
Previously, in The Gazette, Ernst cited her National Guard duty to rebuff criticism about her missing votes, but The Gazette found that only 12 of the 117 missed votes came on days when she was on duty.
The other 105 missed votes represented 57% of the Iowa Senate votes that session.
Ernst's spokesman said she had a better than 90% voting record during her Senate career and that she had never claimed Guard service was the only reason she had missed votes.

In endorsing her for the Republican Primary nomination, the Des Moines Register wrote: "Ernst is a smart, well-prepared candidate who can wrestle with the details of public policy from a conservative perspective without seeming inflexible."

In July 2014, Ernst's campaigning was temporarily paused while she participated in two weeks of National Guard duty.
Also that month, she delivered the Republican Party's weekly address, in which she criticized the health care scandal at the Department of Veterans Affairs and called for a balanced federal budget and entitlement reform.

On August 29, Ernst and Democratic nominee U.S. Representative Bruce Braley announced an agreement to hold three televised debates in Davenport, Des Moines, and Sioux City.
They were held on September 28, October 11 and October 16, respectively.

On October 23, Ernst canceled a scheduled meeting with the Des Moines Register's editorial board, citing as a reason the newspaper's negative editorials about her.
The newspaper's editorial board endorsed Braley.

In the 2014 election, Ernst received $17,552,085 in "dark money", which constituted 74% of nonparty outside spending in her support.

Ernst won the 2014 Senate race, 52.2% to 43.7%.
She is the first woman elected to represent Iowa in either house of Congress.
In July 2013, Ernst announced that she would seek the Senate seat held by retiring Democratic Senator Tom Harkin. Iowa Lieutenant Governor Kim Reynolds endorsed her in October 2013. She was also endorsed by 23 current and former state legislators. In March 2014 former Massachusetts Governor Mitt Romney and former Alaska Governor Sarah Palin endorsed Ernst. In May 2014, the U.S. Chamber of Commerce endorsed her.
Ernst received widespread attention for a campaign advertisement she released in March 2014 in which she made a tongue-in-cheek comparison between her experience castrating pigs and her ability to cut "pork" in Congress. Many found the ad humorous and it was spoofed by late-night comedians, including Jimmy Fallon and Stephen Colbert. Before the ad aired, Ernst had struggled to raise money, and two polls of the Republican primary taken in February 2014 had shown her in second place, several points behind Mark Jacobs. After it aired, a Suffolk University poll in early April showed her with a narrow lead and a Loras College poll showed her essentially tied with Jacobs. By May, she was being described in the media as the "strong front-runner".
In a May 9, 2014, Des Moines Register interview, Ernst said she was "extremely offended" by comments Jacobs made characterizing her as AWOL due to missing over 100 votes in the legislative session ending April 7, 2014. Ernst said, "If [Jacobs] had any sort of service like I have, he would've understood what AWOL means. I have not been AWOL, I will never be AWOL." Previously, in The Gazette, Ernst cited her National Guard duty to rebuff criticism about her missing votes, but The Gazette found that only 12 of the 117 missed votes came on days when she was on duty. The other 105 missed votes represented 57% of the Iowa Senate votes that session. Ernst's spokesman said she had a better than 90% voting record during her Senate career and that she had never claimed Guard service was the only reason she had missed votes.
In endorsing her for the Republican Primary nomination, the Des Moines Register wrote: "Ernst is a smart, well-prepared candidate who can wrestle with the details of public policy from a conservative perspective without seeming inflexible."
In July 2014, Ernst's campaigning was temporarily paused while she participated in two weeks of National Guard duty. Also that month, she delivered the Republican Party's weekly address, in which she criticized the health care scandal at the Department of Veterans Affairs and called for a balanced federal budget and entitlement reform.
On August 29, Ernst and Democratic nominee U.S. Representative Bruce Braley announced an agreement to hold three televised debates in Davenport, Des Moines, and Sioux City. They were held on September 28, October 11 and October 16, respectively.
On October 23, Ernst canceled a scheduled meeting with the Des Moines Register's editorial board, citing as a reason the newspaper's negative editorials about her. The newspaper's editorial board endorsed Braley.
In the 2014 election, Ernst received $17,552,085 in "dark money", which constituted 74% of nonparty outside spending in her support.
Ernst won the 2014 Senate race, 52.2% to 43.7%. She is the first woman elected to represent Iowa in either house of Congress.
Joni Ernst