Iowa primary sets up top Senate battle

Iowa state Sen. Joni ErnstJoni Kay ErnstGOP senator: Trump tariffs are hurting US farmers McConnell: Syria strikes were 'appropriate and measured' GOP senator uncomfortable with ground troops in Syria MORE (R) has won her primary, setting up a key Senate battle against Rep. Bruce BraleyBruce Lowell BraleyOPINION | Tax reform, not Trump-McConnell feuds, will make 2018 a win for GOP Ten years later, House Dems reunite and look forward Trump: Ernst wanted 'more seasoning' before entertaining VP offer MORE (D-Iowa).

The Associated Press has called the race for Ernst, who had 53 percent of the vote with 24 percent of precincts reporting. Conservative radio host Sam Clovis had 19 percent, businessman Mark Jacobs (R) had 17 percent and former U.S. Attorney Matt Whitaker (R) had 9 percent.

By topping the 35 percent threshold, she avoids a primary convention and sets up what could be a close race, and a crucial one in the battle for Senate control. Braley has led in public polling, though not by a large margin.

Ernst had a swift rise to the top of the GOP heap, fueled by a series of memorable ads, a gaffe from Braley, a series of big-name endorsements and quiet backing from Iowa Gov. Terry Branstad (R) and his allies.

The race looked like a sleeper a few months ago as Braley was ahead in the polls and Jacobs had the edge in primary polling due to early and big spending on ads. But that changed when Braley slipped and Ernst went on the air.

Braley was caught on camera deriding Sen. Chuck Grassley (R-Iowa) as a “farmer from Iowa” who was less qualified than him to be on the Senate Judiciary Committee to an audience of Texas trial lawyers. The video set off a furor that forced Braley to apologize and run ads to shore up his standing with farmers and other blue-collar workers.

The next day Ernst dropped her first ad, talking about growing up “castrating hogs on an Iowa farm" and promising to “make ’em squeal” in Washington. The spot went viral just as the race was starting to get more attention due to Braley's gaffe, and an appearance later that week with former Alaska Gov. Sarah Palin (R) helped keep up momentum that she never relinquished. 

Endorsements from former presidential nominee Mitt Romney (R) and Sen. Marco Rubio (R-Fla.) and advertising from the U.S. Chamber of Commerce, Senate Conservatives Fund, and Rubio's leadership PAC helped rocket her past Jacobs.

The big questions going forward are whether Braley can avoid any more major missteps and whether Ernst is prepared for the national spotlight. He'll need to be careful, and she'll need to show she has the policy and fundraising chops for a top-tier campaign.

Ernst pivoted quickly to an attack on Braley after her primary win.

"From day one, Braley has been a rubber stamp for the failed policies of Nancy Pelosi and Barack Obama. And if he makes it to the U.S. Senate he'll be a rubber stamp for Harry Reid. And that’s the last thing Iowa needs," she said in a statement. "This campaign will come down to a very simple choice: Our shared Iowa values, versus Bruce Braley’s liberal Washington values."

Braley touted his middle-class roots after officially winning the nomination to succeed his mentor, retiring Sen. Tom Harkin (D-Iowa).

"As someone who grew up in a working family in Brooklyn, Iowa, worked my way through college and law school here in Iowa, and spent my life representing people from all across our state, I'm deeply honored to win the Democratic nomination for US Senate tonight. I look forward to bringing my campaign to all corners of Iowa in the next five months to discuss my vision to improve the lives of working families and expand opportunities for all Iowans," he said in a statement.

National Republican Senatorial Committee Chairman Jerry Moran (Kan.) congratulated Ernst on her win.

"A mother, a soldier, with a strong agriculture background, Joni Ernst provides just the right contrast with Bruce Braley that Iowans will rally behind," he said in a statement. "Joni Ernst will fight for farmers, for women, and for the Iowa values that have been threatened by the failed policies of President Obama and Washington politicians who've put the agenda of their special interest donors before the needs of the middle class families they were elected to represent."

Democrats quickly blasted Ernst as "hyper-partisan."

"When you peel back Joni Ernst’s unusual ads, you find a rigid, ideological partisan with an agenda that is bought and paid for by outside special interests and out of step with Iowans," Democratic Senatorial Campaign Committee Deputy Executive Director Matt Canter said in a statement. "Her rigid partisanship and support for the federal government shutdown not only won her the support of Sarah Palin, but proved that Joni Ernst is the Sarah Palin of Iowa who would bring more gridlock and dysfunction to Washington."

This post was last updated at 11:35 p.m.