SALT LAKE CITY — The conflict between Utah's governor and state Legislature escalated Thursday after Rep. Jason Chaffetz officially announced his plans to leave Congress, with legislative leadership threatening legal action over how the vacancy is filled.

Gov. Gary Herbert has said he will not call a special session of the Legislature for state lawmakers to set the process for replacing Chaffetz, R-Utah, when he steps down June 30.

In response, Senate President Wayne Niederhauser, R-Sandy, issued a statement warning Herbert that "the path forward with the least amount of legal risk would be for the governor to call a special session to allow lawmakers to add appropriate election language to the state code."

Niederhauser also cited Article I of the U.S. Constitution as evidence that "the times, places and manner of our elections are clearly a legislative responsibility," a contention echoed by Greg Hartley, chief of staff for House Speaker Greg Hughes, R-Draper.

"This is a separation of powers issue," Hartley said in statement. "The House and Senate majority caucuses are unanimous in their support for a special session."

Hughes is "committed to defending the legislative process and calls on Gov. Herbert to convene a special session of the Legislature to vote a clearly defined process into law,” Hartley said.

Paul Edwards, Herbert's deputy chief of staff, said the governor believes "that the risk of legal challenge is actually mitigated by following the clear and current law as the Legislature has enacted it in Utah code."

Herbert, speaking with media at KUED's monthly news conference earlier Thursday, said special sessions are designed for issues where there is "unanimity" and broad consensus, which he says is not the case with how to handle the pending vacancy.

"We don't even have consensus for what legislators want to pass in a special session," he said. "We ought not to have a free-for-all."

The governor's office said it received an official notice from Chaffetz of his resignation, which now allows Herbert to issue the "call" for a special election.

Herbert said state and federal laws specify that the governor "shall" call for a special election under such circumstances, adding that he believes the process could play out within an 180-day window in which a primary and general election could be held to select the eventual replacement.

"Utah voters must have access to the ballot if there is an election," he said.

GOP lawmakers and their Democratic counterparts have vowed to fight Herbert on the selection process for a candidate. Rather than the signature-gathering process, they want political party delegates to nominate candidates.

Herbert insisted that hastily crafting an election reform bill during the tight time constraints of a special session is not the way to handle something that should be a deliberative process.

He noted that a past Legislature had the "wisdom" to acknowledge the rarity and unique circumstances posed by a sudden congressional seat vacancy and adopted a law giving the executive branch "flexibility" to deal with the challenge.

"I want to do the right thing for the right reasons," Herbert said, emphasizing that the process has to be one with integrity that serves the voting public.

Chaffetz also weighed in on the process for picking his replacement, saying he supports the governor's approach.

Chaffetz said he has worked closely with the governor’s office, and the path Herbert has settled on allows the special election to be held with this year’s municipal elections. He said that would minimize the cost and shorten the time to replace him.

“I don’t believe you dramatically change the process from what is the current law right in the middle of an election,” Chaffetz said. “If the Legislature wants to move a different direction or have special rules for a special election, I think they could have and should have done that a long time ago.”

The 2017 Legislature looked at fleshing out the law when Rep. Chris Stewart, R-Utah, was being considered for secretary of the Air Force, an appointment that would have created the state's first congressional vacancy since 1929.

A Senate bill that called for holding a special election similar to the regular process was replaced in the House by a plan letting political parties nominate candidates, and in the final hours of the session, it failed to pass.

State Elections Director Mark Thomas said once the governor issues the call for a special election, the responsibility of crafting how that election plays out — and its supervision — falls to Lt. Gov. Spencer Cox.

"Absent any other direction from the Legislature, we have to determine what that process is to fill that vacancy," Thomas said.

A stand-alone election to fill Chaffetz's seat would cost $1 million for a primary and another $1 million for a general election, he said.

"If you tie it to an existing election, there is very little cost," Thomas said.

While it would be a scramble, Chaffetz's successor could be on the ballot for the Aug. 15 municipal primaries in the 3rd District, with final selection of a candidate in November's general election.

Those vying for candidacy would have to meet the standard eligibility requirements and collect 7,000 signatures to get on the primary ballot.

The 3rd District has 352,000 registered voters spread out through five counties — San Juan, Emery, Grand, Carbon, Wasatch — most of Utah County, including Provo, and the east side of Salt Lake County. The district covers more than 50 municipalities, and there are no geographic distribution requirements regarding the signatures.

Chaffetz's departure, rumored for a lucrative broadcasting deal with Fox News, has riled some GOP lawmakers who are angry that a possible quest for money is putting the party in such an untenable position.

"If it is just to go on to a different job, a more lucrative job, that will be very offensive to me" and other lawmakers, Niederhauser said Wednesday.

That lawmakers are scrambling to respond to Chaffetz's expected departure shouldn't be a surprise.

The last time the issue came up in Utah politics was 1929, when a sitting representative died while in office, Herbert said. At the time, the representative died in December and political leaders opted to wait until the next election — the following November — to fill the vacancy.

Thomas said the cost associated with holding a stand-alone election dominated the debate, especially given it was shortly after the stock market crash leading to the start of the Great Depression — the largest global economic crisis of the 20th century.

When it comes to party delegates picking potential replacements for Chaffetz or a special election, it appears the governor has public opinion on his side.

A new UtahPolicy.com poll shows that 76 percent of Utah voters prefer candidates selected by an election process rather than by party delegates.

The Alliance for a Better Utah issued a statement Thursday in support of Herbert's stance on a special election.

“We are grateful the governor is placing an emphasis on allowing voters to be involved in choosing their next representative," said Chase Thomas, policy and advocacy counsel for the government watchdog group.

"As this unfolds over the coming weeks, our hope is that this election is conducted transparently, with fairness for all involved, and that any disagreements will be solved quickly so that the constituents of District 3 will soon have a new congressman representing them in Washington, D.C.”

Contributing: Dennis Romboy, Jared Page