BILLINGS, Mont. (AP) — Montana voters on Tuesday were choosing party nominees for governor, U.S. Senate and House and a slate of other offices in a primary election that was changed to all-mail balloting to protect against the spread of the coronavirus.

Voters had turned in a record 353,129 ballots through noon Tuesday, which is nearly 59,600 more than the 293,548 cast in the 2016 primary, according to the secretary of state. Ballots were still being accepted by county election officials through 8 p.m. Tuesday.

The Republican and Democratic primaries for governor topped the list of competitive races, which featured five open statewide offices with elected officials either termed out or deciding to run for a different position.

Republicans are seeking to end 16 years of Democratic domination of the governor’s office when Steve Bullock completes his second term at the end of the year. U.S. Rep. Greg Gianforte and Attorney General Tim Fox were competing in the Republican primary. Democrats seeking the nomination are Lt. Gov. Mike Cooney and first-time candidate Whitney Williams.

For Gianforte, a former technology entrepreneur who was first elected to the state's only House seat in 2017, it’s his second run for governor. He lost to Bullock in 2016. Fox is ending his second term as attorney general, a post he won in a landslide in 2016. He successfully battled colon cancer two years ago.

Cooney, a former legislator and secretary of state, has campaigned on building on the successes of Bullock’s tenure. Williams, a businesswoman who is the daughter of former U.S. Rep. Pat Williams and former state Sen. Carol Williams, has drawn on her deep political connections and fundraising experience to build a strong campaign that’s challenged Cooney.

Bullock defeated first-time candidate John Mues for the Democratic nomination to challenge incumbent Republican U.S. Sen. Steve Daines.

Daines, a first-term senator, defeated Daniel Larson and John Driscoll in Tuesday’s GOP primary.

That race is expected to have a high national profile in the fight for party control of the Senate.

Republicans including State Auditor Matt Rosendale and Secretary of State Corey Stapleton were competing for the nomination for Gianforte’s open House seat. Former state Rep. Kathleen Williams, who lost to Gianforte in 2018, is seeking the Democratic nomination again, this time against state Rep. Tom Winter.

Rosendale’s and Stapleton’s open seats have led to competitive Republican primaries. Two Democrats and two Republicans are competing for their parties’ nominations to succeed the termed-out Fox as attorney general.

Former Vice President Joe Biden won the Democratic nomination for president after the two other candidates on the ballot, Sens. Bernie Sanders and Elizabeth Warren, dropped out and endorsed Biden.

President Donald Trump ran unopposed for the Republican nomination.