Despite a crowded field of Republicans seeking to unseat U.S. Sen. John Cornyn, voters are well-served to support him for a third term.Within a decade of his first election, Cornyn emerged as a party leader in the Senate, quickly climbing to the position of minority whip — a role in which he wields tremendous influence in the 100-member body. While several of his primary opponents articulately express what they see as Cornyn’s complacency in supporting an all-too-powerful federal government, none can be considered a serious challenger.The seven candidates seeking to unseat Cornyn are hotel industry executive Curt Cleaver; aerospace consultant and retired Army officer Ken Cope; small-business owner Chris Mapp; retired Air Force officer Reid Reasor; Houston-area U.S. Rep. Steve Stockman; business owner Dwayne Stovall and immigration attorney and small-business owner Linda Vega.Their respective platforms vary in depth and focus, but their ideological underpinnings are largely indistinguishable. Each opponent sees Cornyn as an impediment to the restoration of constitutionally limited government.These concerns are misplaced on a candidate with high-caliber conservative credentials.Cornyn’s detractors have criticized him for abandoning Texas’ junior senator, Ted Cruz, in the fight to defund the president’s unpopular healthcare law. But Cornyn has either introduced or co-sponsored bills to repeal and defund Obamacare in one capacity or another at least 29 times.Cruz’s filibuster eventually shut down the government for 16 days, a move that coincided with historically low approval ratings for Congress. During the government closure, Cornyn donated what he would have earned to three Texas charities. The gesture was small, but speaks volumes about his character.Revealing his measured approach to solving policy crises, Cornyn likened the shutdown effort to “burning down the house to get rid of the mice or rats.”The shutdown dispute and many others within the party are more about tactics than ideology. And Cornyn’s dozen years in the Senate have taught him a thing or two about effective policymaking, not just effective politicking.Stockman is Cornyn’s best-known challenger, but he seems to be struggling to run an effective campaign while adequately representing the state’s 36th District.Stovall has garnered significant Tea Party support and presented some serious policy proposals, as has Cope, who released a tax plan last week. Vega spoke thoughtfully of the GOP’s need to engage minority communities in an interview with the Star-Telegram Editorial Board. These candidates are smart and accomplished but lack the public policy experience necessary to serve the state in Congress’ “deliberative” body.As a member of Senate leadership, Cornyn certainly represents the party “establishment” — a dirty word for many Texans. But those who grumble that Cornyn is “not conservative enough” do conservative values a disservice.If Republicans in Texas take the long view, they will see that the party can best effect change by gaining seats in the Senate chamber, at which time leaders like Cornyn will be well-positioned to make the changes they believe are needed in Washington. The Star-Telegram Editorial Board recommends John Cornyn in the Republican primary for U.S. Senate.