Rep. Abby Finkenauer introduces Democratic presidential candidate Joe Biden on January 3, 2020, in Independence, Iowa.
CNN  — 

A judge in Iowa ruled on Sunday that Democratic Senate candidate Abby Finkenauer cannot appear on the state’s June 7 primary ballot, dealing a significant blow to her already long-shot hopes of unseating Republican Sen. Chuck Grassley.

Finkenauer pledged Monday to “challenge this deeply partisan decision to the Iowa Supreme Court.”

On Sunday night, Polk County District Judge Scott Beattie ruled that Finkenauer’s name “shall not be included on the primary ballot for the Democratic Primary for U.S. Senate.”

The ruling centers around a dispute over the signatures required to get on the ballot. Although Finkenaur’s campaign submitted more than the necessary 3,500 signatures, the judge found that she did not meet the requirement that each candidate have at least 100 signatures from at least 19 Iowa counties due to questions about three signatures obtained from Allamakee and Cedar counties.

“The Court takes no joy in this conclusion,” Beattie wrote. “This Court should not be in the position to make a difference in an election, and Ms. Finkenauer and her supporters should have a chance to advance her candidacy. However, this Court’s job is to sit as a referee and apply the law without passion or prejudice. It is required to rule without consideration of the politics of the day.”

Finkenauer initially responded to the decision by saying her campaign was “exploring all of our options to fight back hard.” Later on Monday, Finkenauer announced she would challenge the decision with the Iowa Supreme Court.

“We refuse to back down in the face of these partisan attacks,” she said. “We are confident that we have met every requirement to be on the ballot, and we will not stop fighting back against this meritless attack that seeks to silence the voices of tens of thousands of Iowans.”

Although Finkenauer has blamed Republicans for her signature issues, Democratic operatives in Iowa have been quietly aghast at how a statewide candidate, let alone someone who successfully ran for Congress recently, cut it so close on the signatures needed to make the ballot.

The success of Finkenauer’s challenge will now rest with seven justices on Iowa’s highest court – only one of whom was appointed by a Democrat.

If Finkenauer’s challenge is unsuccessful, the former congresswoman could accept the ruling and run as a write-in candidate in the June primary. This could be complicated by the fact that although Finkenauer, a former congresswoman, was the front-runner in the Democratic field, she is running against two other Democrats: Glenn Hurst, a city council member in Minden, Iowa, and Mike Franken, a retired Navy admiral.

Republicans have been challenging Finkenauer’s signatures, initially bringing the complaint to the State Objections Panel. The state body decided in March that Finkenauer could stay on the ballot, but just narrowly. The panel found that Finkenauer submitted at least 100 signatures from 20 counties and needed 19. One of those counties was knocked out by the objection but she was able to squeak by with 100 signatures in one challenged county and 101 in two others.

But Republicans successfully brought this lawsuit, saying the panel incorrectly interpreted the law.

Iowa Republicans celebrated the decision on Monday, with Republican Party of Iowa Chairman Jeff Kaufmann arguing that the questions surrounding Finkenauer’s signatures shows a “severe lack of enthusiasm behind Iowa Democrats.”

“Not qualifying for the ballot is a complete and utter embarrassment,” Kaufmann said.