Conservative groups and activists have urged Liljenquist to run against Hatch, believing the policies the U.S. senator has advocated during his 36 years in Washington have expanded the reach of government and increased the debt.
Hatch's campaign manager, Dave Hansen, said he assumes Liljenquist will get into the Senate race, and he has indicated several times that was the way he was leaning.
"We'll have to wait and see what he decides to do, but it's too bad he didn't honor his commitment to the people of his state Senate district to complete his term there, his first and only term," Hansen said.
Hatch is campaigning aggressively and has been for months, Hansen said.
"When it comes right down to it, the voters of Utah are going to elect [Hatch] to serve another term because of what he can do in the positions he will be in," Hansen said. If Republicans take over the Senate, Hatch could become chairman of the powerful Senate Finance Committee.
Utah law prohibits legislators from raising money for any campaign during the 45-day legislative session, which begins in late January. Liljenquist has said previously that he would resign if he was going to run for Senate.
Quin Monson, associate director of the Center for the Study of Elections and Democracy, said it's hard to gauge whether Liljenquist can tap into the same delegate frustration that led to the ouster of Sen. Bob Bennett last year.
"He's starting late, and it's hard to tell who the delegates will be in advance and if they'll be as grumpy as they were last time," he said. "I think Hatch is being more aggressive, he's had more time to reach out, and it may be that the unhappiness reached its peak with Bennett."
State Rep. Chris Herrod, R-Provo, said Thursday he is still considering running against Hatch and will make up his mind after the holidays.
Democratic Rep. Jim Matheson's announcement on Thursday that he would seek re-election in the 4th Congressional District leaves open a possibility that Liljenquist could run in the 2nd Congressional District, which includes the area of Davis County where he lives.
Asked about that possibility, Liljenquist chuckled and said to wait for his announcement next month.
Liljenquist submitted his letter of resignation to Senate President Michael Waddoups, R-Taylorsville, Thursday evening. It was effective immediately.
"I want the people of south Davis County to have a chance to choose a new senator to represent them in the next legislative session," Liljenquist said.
Thursday night, Liljenquist launched a vague website, itstimeutah.com, which has a standard political campaign front page.
Several Davis County Republicans, anticipating Liljenquist's departure, have already started jockeying to replace him. Among them are former Utah Republican Party Vice Chairman Todd Weiler; Randy Shumway, the CEO of the Cicero Group, a polling firm; and Greg Ericksen, a businessman who has sought for years to build a movie studio in Summit County. Others also could join the fray.
Liljenquist won an election to replace the late Sen. Dan Eastman when he retired in 2008. Liljenquist sponsored legislation reforming the state's pension system, moving it toward a modified 401(k) system, after the nation's economic collapse punched a hole in the retirement fund.
Last session he sponsored legislation to streamline the state's Medicaid program, although the state is still awaiting word from the U.S. Department of Health and Human Services as to whether it will receive a waiver to implement the measures.
Last month, Liljenquist was named "Legislator of the Year" by Governing magazine.
"I have so enjoyed serving in the state Legislature and there are millions of problems [to solve], but I also trust my colleagues. We have a great Legislature that is very deliberative and very careful," he said. "We've realized some important goals the last few years, and I look forward to watching the state continue on its trajectory of fiscal solvency."
Liljenquist, 37, is a graduate of the University of Chicago Law School and was a consultant with Bain and Company. He started Focus Service, a Utah-based call center. He sold that company and works for a consultant on pension reform.
He and wife Brooke have six children age 11 and younger.