(AP Photo/The Des Moines Register, Charlie Litchfield)

This post has been updated.

Republican Senate candidate Joni Ernst snubbed The Des Moines Register, Iowa's biggest and most influential newspaper, by canceling her scheduled Thursday endorsement interview with the editorial board.

Ernst was scheduled to sit down with the Register for one hour on Thursday in advance of the paper's endorsement, which could come Sunday. Her Democratic opponent, Rep. Bruce Braley, met with the board earlier this month.

Ernst's decision to skip out on the Register prompted public criticism from the paper's publisher and a prominent columnist. Publisher Rick Green said in a statement:

“We were disappointed by the Ernst camp’s decision to not spend an hour with the editorial board and share her vision for our state and the rest of the country. This has been an incredibly nasty, competitive race where both sides have spent millions and aired tens of thousands of TV spots. Undecided voters I talk to want Sen. Ernst to break through the rhetoric and cacophony of campaign ads about hogs, Obamacare and balanced budgets. It’s a time for sharing specifics. It’s a chance to have a serious conversation about vision, priorities, the economy, national security, foreign relations and Social Security. I’m not angry she snubbed the Des Moines Register editorial board, which is in final deliberations about our Senate endorsement. It truly isn’t about us. We wanted to discuss the future of the state and allow Joni Ernst to share insights and specific responses to the concerns and questions of Iowans and voters. It’s unfortunate that cannot happen.”

Rekha Basu, a Register columnist, wrote on Facebook, "Is Joni Ernst afraid of newspaper editorial boards? After much negotiating, she was scheduled to meet his morning with writers and editors at The Des Moines Register, but last night her people called to unilaterally cancel. She has also begged off meetings with The Cedar Rapids Gazette and The Dubuque Telegraph-Herald."

Earlier this week, Basu wrote a column critical of Ernst headlined, "This isn't the Iowa woman we should elect." Basu has a son who is involved with Braley's campaign. But Green said that Basu is not a member of the editorial board and that her son's work with the Braley campaign "is not a factor in our endorsement process."

Ernst cancelled the Register endorsement interview because she believed the paper's editorial board had shown a bias against her in editorials over the past two months, according to a campaign official. The editorial board has criticized Ernst for her comments about poverty; her stance on "nullification"; and her support as a state senator for a measure that would add a "personhood" amendment to the Iowa Constitution.

"We already knew where the editorial board was -- all negative on Joni," said the official, who requested anonymity to speak candidly about the situation. "Why would we go in there? We knew how this was going to play out."

In a statement, Ernst campaign spokeswoman Gretchen Hamel said:

"Joni is barnstorming the state, visiting all 99 counties and  talking face to face with voters about the issues they care about most. Recent editorials in the Des Moines Register make their position in this race perfectly clear, and it's one that many voters across our state seem to disagree with. With less than 12 days to go, time is precious and Joni  wants to spend every minute talking to undecided voters, hearing their concerns, and demonstrating why we need a change in Washington."

The contest between Ernst and Braley is one of the closest and most contentious Senate races in the country. Ernst leads Braley by 2.5 percentage points in an average of polls by Real Clear Politics. Democratic and Republican strategists agree that Iowa could determine which party controls the Senate.

The Register has a history of endorsing both Democratic and Republican candidates. In 2012, the Register endorsed Republican presidential nominee Mitt Romney over President Obama, although it backed Obama in 2008. On Thursday, the Register endorsed Republican David Young over Democrat Staci Appel for Congress in Iowa's third congressional district, one of the closest House races in the country. In May, the Register endorsed Ernst in the competitive, multi-candidate Republican primary.

Green said the Register's editorial board "won't make our endorsement decision based on Ernst's decision to not meet with the edit board, just like we wouldn't endorse Braley merely because he met with us.

"Snubbing us or appearing before us won’t be the final call in our endorsement," Green added. "This is too important of a race to let petty things like that affect our endorsement process. But we are disappointed she didn’t come in today.”