The Wisconsin Supreme Court on Monday blocked Gov. Tony Evers' executive order to postpone in-person voting for the state's presidential primary set for Tuesday.

The Democrat aimed to delay voting until June 9 because of the coronavirus pandemic. In a 4-2 ruling, the court said Evers did not have the authority to move the election.

Earlier Monday, the governor cited safety as he pushed to postpone in-person voting.

"As municipalities are consolidating polling locations, and absent legislative or court action, I cannot in good conscience stand by and do nothing," Evers said in a statement from his office. "The bottom line is that I have an obligation to keep people safe, and that's why I signed this executive order."

Later on Monday, the U.S. Supreme Court voted 5-4 along partisan lines to reverse a lower court order that extended the deadline for absentee ballots in the state. A federal appeals court on Friday had upheld a one-week extension, but state and national Republicans urged the justices to do away with it.

The execution of Wisconsin's primary has been in a tug-of-war between Republican and Democratic legislative members for weeks, with Evers, a Democrat, proposing key changes to allow people to avoid in-person voting due to the spread of the outbreak. GOP members have opposed the moves.

Last week, Evers called for a special legislative session just days before the state's original primary date to cancel the in-person portion of voting. He said the state aimed to shift to an all-mail voting system for the primary with a deadline of May 26 to get ballots in. But the effort got shut down.

Republican legislative members in Wisconsin have been keen on pushing back against any effort to postpone elections because a key statewide race, if postponed, could loosen their grip on the judiciary. A Republican candidate is running in the race for a state Supreme Court seat, and Republicans fear that adjustments to the election could bring more favorable outcomes to the Democratic candidate on the ticket.

Wisconsin, with 84 pledged presidential delegates, would have joined a list of more than a dozen states and U.S. territories that have adjusted their nominating contests due to the coronavirus, with some opting for a mail-in system to replace in-person voting and others delaying the primaries entirely. The moves have upended the Democratic primary between former Vice President Joe Biden and Sen. Bernie Sanders of Vermont.

Both campaigns no longer do in-person events or rallies and have been relying on digital outreach to connect with voters.

Biden maintains a commanding lead over Sanders, having secured victories in most of the completed primaries. In March, Sanders was mulling his options, his campaign said in an email, but he has since given no indication he is ready to drop his bid.

Biden was the clear winner at the last nominating contests, which were held on March 17.

The coronavirus, which is believed to have originated in Wuhan, China, has spread to dozens of countries globally, with more than 1.3 million confirmed cases worldwide and over 72,638 deaths so far, according to data from Johns Hopkins University. There are at least 347,003 cases in the United States and at least 10,335 deaths, according to the latest tallies.

— CNBC's Tucker Higgins contributed to this report.