U.S. Rep. Steve Stockman packed a lot into one sentence Monday.“Liberal John Cornyn wakes up every morning and works to make the Senate a more liberal place,” Stockman, from Clear Lake, near Houston, said in announcing his plan to challenge Cornyn in the March 4 Republican primary. Cornyn is the Senate minority whip and thus one of the nation’s most powerful Republicans, but there were those three words: “Liberal John Cornyn.”Not many Texans would have thought of their senior senator as “liberal,” at least not until a little more than a year ago. That was when the man who is now the state’s junior senator, Ted Cruz, showed how to use the liberal label liberally and effectively in defeating a more entrenched political opponent who was merely conservative.And with those three words, Stockman captured what this primary will be about for Texas Republicans. It will be a struggle between the right and the far-right to define the party’s identity.For Democrats, the March primary will see some contests, but none so bitter as those between Republicans. The Dems have more at stake in November’s general election, when they’ll be struggling to prove they’re still relevant in the Lone Star State.Stockman isn’t the perfect candidate to run against Cornyn, although he’s established in far-right GOP and claims kinship with Tea Party favorites like Cruz and Kentucky Sen. Rand Paul.He once was arrested with Valium in his underwear (the charges later were dropped), lived at the Fort Worth Water Gardens for about six months in his twenties (he’s now 57) and has a reputation for hyper-dramatic statements (“You and I are in a foxhole fighting to save this constitutional Republic,” he said Monday in announcing his run for the Senate, “but liberal John Cornyn is bayoneting us in the back.”)But he can point to “a 100% pro-gun, pro-life, conservative voting record.”And he can lay into Cornyn for declining to stand behind Cruz in shutting down the federal government earlier this year.There seems little chance he can match Cornyn’s funding — nearly $7 million in cash on hand as of Sept. 30. But Stockman has launched a grassroots fundraising campaign, and he could get backing from major conservative groups.Matt Hoskins, executive director of the Senate Conservatives Fund, said his group has not decided whether to endorse Stockman, “but we’re glad he is running.”He added, “Texas deserves two conservative fighters in the Senate, not just one. John Cornyn has voted to increase the debt, raise taxes, bail out Wall Street banks, and fund Obamacare. He’s part of the problem in Washington and voters deserve an alternative.”Other alternatives will face Texas Republicans. While Attorney General Greg Abbott seems a shoo-in for the party’s nomination for governor, conservative vs. more-conservative is the name of the game in the race for lieutenant governor. Incumbent Lt. Gov. David Dewhurst, who lost the Senate race against Cruz last year for not being conservative enough, has three strong challengers who can come at him from the right.At least four other statewide races will be hot contests for the GOP.