PORTLAND, Maine — The 10-candidate field for U.S. Senate is set for the June 12 primary after no one decided to challenge petitions filed by six Republicans and four Democrats seeking to get on the ballot, but Democrats are trying to knock one Republican U.S. House candidate off the ballot, officials said Friday.

A challenge by Lizzy Reinholt, spokeswoman for the Maine Democratic Party, found fault with 15 petitions submitted by Kevin Raye, a Republican running in the 2nd Congressional District, including the master petition that was filled out by a town official. Reinholt, who lives in the 2nd District, said that could invalidate all of the 1,000-plus petitions submitted on behalf of the state Senate president.

The problem was that 15 of the circulator’s oaths were filled out incorrectly, with the circulator failing to note party affiliation, she said.

“It’s definitely a sophomore mistake for someone who’s run for office as many times as he has,” Reinholt told The Associated Press.

Raye, who’s seeking to unseat Democratic Rep. Mike Michaud, said the word “Republican” is missing from one location but appears in two other places on the challenged petitions.

“This challenge makes one point clear: The Maine Democratic Party is very uneasy about a Raye-Michaud matchup in November,” Raye said in a statement.

An administrative hearing on Reinholt’s challenge will be scheduled within seven days, said Megan Sanborn, spokeswoman for the secretary of state’s office.

Challenges also were filed before Thursday’s deadline against Nichi Farnham in State Senate District 35 and Stuart Pennels in House District 111.

There were no such challenges in the U.S. Senate race, where candidates scrambled to collect signatures after Republican Sen. Olympia Snowe announced she wouldn’t seek a fourth term. That means the Senate primary ballot is settled unless someone drops out.

The Republican Senate candidates are Attorney General William Schneider, Treasurer Bruce Poliquin, Secretary of State Charlie Summers, small-business man Scott D’Amboise, state Sen. Debra Plowman and former state Sen. Rick Bennett. Democrats are former Secretary of State Matthew Dunlap, state Sen. Cynthia Dill, Rep. Jon Hinck and Portland home builder Ben Pollard. Also in the race are several independents, including former Gov. Angus King.

In Maine’s congressional races, Raye and Republican Blaine Richardson of Belfast are vying to challenge Michaud in the 2nd District.

In the 1st District, Democratic U.S. Rep. Chellie Pingree will face one of two Republicans, Senate Majority Leader Jon Courtney or Patrick Calder, a Portland mariner.