No challenger managed to beat an incumbent Utah legislator in party conventions this year. However, lawmakers are leaving voluntarily in near-record numbers.

As the convention season ended over the weekend, 24 incumbents are now leaving office out of 90 legislative seats up for election this year — and all of them are departing voluntarily.

Incumbents survived every challenge they faced at conventions, although four were sent to primary election showdowns.

Even four of the five current lawmakers who sought other offices survived convention challenges. The only one defeated — current Rep. LaVar Christensen, R-Draper — was topped by another incumbent, Rep. Dan McCay, R-Riverton, in a state Senate race.

Adam Brown, a political science professor at Brigham Young University, has compiled data about how many freshmen entered the Utah House every year back to statehood (but he did not do the same for the Utah Senate).

(Leah Hogsten | The Salt Lake Tribune) Utah House of Representatives District 30 candidate Fred Cox sets up his signs in the commons area at the Salt Lake County Republican Party Organizing Convention at Cottonwood High School, Saturday, April 14, 2018.

So far this year, 18 House members decided not to seek re-election, meaning the 75-member House will have a minimum of 24 percent turnover.

Over the past quarter-century, “only 2013 had more turnover [27 percent] than we are guaranteed to see for 2019” in the House, Brown noted.

“If two more House incumbents fail to return — either because of primary or November losses — then we would tie 2013,” he said. “If three or more fail to return, then we’ll have the most turnover since 1993,” which had 36 percent turnover.“

In the most recent big turnover year of 2013, several of those hitting the exits did so because redistricting was pitting them against other incumbents, Brown said.

Also, numerous members of the conservative Patrick Henry Caucus that year decided to run for higher office, Brown observed, “and nearly all are out of politics as a result.”

He sees nothing like that this year, and no overriding reason for the large number of departures.

Some left because of age (such as 80-year-old Sen. Pete Knudsen, R-Brigham City), some because they are moving (such as Rep. Justin Fawson, R-North Ogden), some left after long service (such as Senate President Wayne Niederhauser, R-Sandy, and Rep. Mike Noel, R-Kanab), and several decided to run for other offices.

Nationally, Congress is seeing a high number of retirements, but Brown says that is likely for different reasons — especially because of low approval ratings of President Donald Trump that complicate re-election by fellow Republicans in midterm elections. Brown does not see that as a factor in Utah’s GOP-dominated legislative races.

“In Congress, people are afraid it’s not worth the fight,” Brown said. “Outside of a handful of districts, I don’t know that’s the case with most of these open seats” in the Utah Legislature.

He listed a few examples in which incumbents perhaps retired to avoid a tough and potentially embarrassing fight for re-election.

That includes Christensen switching to run for the state Senate and losing. “He saw the handwriting on the wall” in his own House district, Brown said, after Christensen had won two years ago by just five votes.

Al Hartmann | The Salt Lake Tribune Rep. LaVar Christensen, R-Draper, sponsor of the legislative organization amendment bill, listens as Democrats urge a "no" vote on the house floor Tuesday, Feb. 23.

Two incumbents also withdrew just before conventions as they faced spirited campaigns by challengers who raised more money: Sen. Margaret Dayton, R-Orem, said she resigned for medical reasons; Rep. Lynn Hemingway, D-Millcreek, who missed the entire legislative session this year to be with his wife, who became sick in New York City, said he pulled out because of her ongoing illness.

Among the four incumbents forced into the June 26 primary is newly appointed Sen. Brian Zehnder, R-Holladay, who sided more often with Democrats this year in party-line votes than his own party, upsetting some GOP members in one of the state’s few true swing districts where either party could win.

Also landing in a primary is Rep. Christine Watkins, R-Price, who switched from being a Democrat a few years ago. She faces Carbon County Commissioner Jae Potter. House budget chairman Brad Last, R-St. George, faces Mark Borowiak, a substitute teacher.

Rep. Ray Ward, R-Bountiful, was forced into a primary because of an unusual rule in Davis County to punish candidates like him who also gathered signatures to qualify for the ballot. Instead of needing the usual 60 percent of delegate votes to clinch the nomination at convention, he was required to win 70 percent. Ward won 66 percent, so he will face former state GOP Vice Chairman Phill Wright in the primary.

FILE - In this Jan. 23, 2018, file photo, Republican state Rep. Ray Ward talks on the House floor, in Salt Lake City. Utah's House of Representatives has passed legislation barring abortions sought because a fetus has been diagnosed with Down syndrome. Ward unsuccessfully tried to amend the bill to require that the state pay $1.8 million annually to provide services to people with Down syndrome. (AP Photo/Rick Bowmer, File)

Even though primary and general elections are yet to come, it’s all over but the shouting for Reps. Corey Maloy, R-Lehi, and Marc Roberts, R-Salem, after they eliminated their only challengers at convention. Four others had no one file against them at all: Sen. Stuart Adams, R-Layton, and Reps. Brian King, D-Salt Lake City; Adam Robertson, R-Provo; and Travis Seegmiller, R-St. George.

Five other incumbents now face challenges only from minor party or unaffiliated candidates: Reps. Walt Brooks, R-St. George; Kay Christofferson, R-Lehi; Val Peterson, R-Orem; Robert Spendlove, R-Sandy; and Lowry Snow, R-Santa Clara.

Why are incumbents so successful? Brown said it has been well researched through the years by political scientists.

“The first factor is some people are politically capable and others are not. The fact that somebody became an incumbent tells you they already are the politically capable type,” he said. “Some challengers can’t give good speeches, they don’t know how to organize delegates, they don’t know whom to hire. Incumbents generally do.”

Also, “There is the scare-off effect. The people who are politically talented,” such as city council members, mayors or political activists, “are more likely to sit it out because they can see there’s a capable incumbent in place who is willing to fight,” and it makes more sense to “wait for an open seat or when there is a clear vulnerability.”

Finally, incumbents raise campaign contributions without even trying, Brown says.

“Most donations come from organized interests,” he said. “And most organized interests are less concerned about who wins a race than about being on the good side of those who win.”