Duncan is considered a [[Moderate Republican]]. Along with colleagues Bob Deuell of Greenville, John Carona of [[Dallas]], Kevin Eltife of Tyler, and Kel Seliger of [[Amarillo]], he was named in 2013 among the most [[liberal]] members of the then nineteen Senate Republicans, according to an analysis by Mark P. Jones of [[Rice University]] in [[Houston, Texas|Houston]]. Jones also found that these Republicans saw passage of 90 percent of the bills for which they had voted.<ref>{{cite web|url=http://lubbockonline.com/interact/blog-post/enriquerangel/2014-02-24/why-state-sen-kel-seliger-has-republican-primary#.Uxt638uPIfh|author=Enrique Rangel|title=Why state Sen. Kel Seliger has a Republican primary challenger|date=February 24, 2014|publisher=''Lubbock Avalanche-Journal''|accessdate=March 8, 2014}}</ref> In the 2014 primaries, Carona was narrowly defeated, and Deuell narrowly lost a runoff contest with fellow Republican and the more [[conservative]] Bob Hall.<ref>{{cite web|url=https://team1.sos.state.tx.us/enr/results/mar04_169_state.htm?x=0&y=218&id=176|title=Republican primary election returns, March 4, 2014|publisher=enr.sos.state.tx.us|accessdate=March 6, 2014}}</ref>
After four years as the fourth chancellor of the Texas Tech System, Duncan suddenly announced his retirement on August 13, 2018, effective August 31. In his four years time at the helm, Duncan raised more than $585 million in philanthropic funds. The system endowment has grown to a total value of $1.3 billion. Records were established in degrees awarded, student enrollment, and expenditures on faculty research. In his retirement announcement, Duncan said serving the system has been the highlight of his career in public service. “As we approach the start of a new school year, I look back with pride on the tremendous strides we have made in recent years. But I have also reflected on my life, my decades of public service, and realize that, at 65, it’s time to retire, move on, and begin to tackle new challenges," Duncan said.<ref>{{cite web|url=http://www.lubbockonline.com/news/20180813/chancellor-duncan-retiring-from-texas-tech-system|title=Chancellor Duncan retiring from Texas Tech System|publisher=''Lubbock Avalanche-Journal''|date=August 13, 2018|author=Sarah Self-Walbrick|accessdate=August 17, 2018}}</ref>
Reports by the ''Lubbock Avalanche-Journal'' contend that the regents in a 5-4 vote expressed "No confidence" in Duncan continuing as the chancellor. Speculation persists that his unfavorable evaluation came from fallout over his plan to build a second state [[Veterinarian|veterinary]] medical school in Amarillo. The existing veterinary school is at [[Texas A&M University]] in College Station, which opposes building a second such facility. Republican Governor [[Greg Abbott]] denied rumors that he was behind the regents' decision to give Duncan a "No confidence" vote.<ref>{{cite web|url=http://www.lubbockonline.com/news/20180815/abbott-denies-rumors-of-involvement-in-texas-tech-chancellor-duncans-retirement|title=Abbott denies rumors of involvement in Texas Tech Chancellor Duncan's retirement|publisher=''Lubbock Avalanche-Journal''|date=August 15, 2018|author=Matt Dotray|accessdate=August 17, 2018}}</ref>