The 2018 election season begins in earnest Saturday, when candidates across the state begin officially filing for office.

Texas Gov. Greg Abbott will highlight the first day of action. He's scheduled to turn in his paperwork to election officials at an Austin American Legion, where he'll also unveil his "Front of the Line" plan for veterans.

Abbott's haste in filing his candidacy is understandable. The incumbent is not expected to receive a serious challenge in the March Republican primary. In fact, no Republican statewide official is expected to face a major challenge.

Much of the action will swirl around Texas legislative races, including several high-profile Senate contests in North Texas.

The retirements of several Republican members of the U.S. House has created rare openings in Texas' congressional delegation. And Rep. Pete Sessions has drawn several Democratic Party contenders for his Dallas-anchored House seat.

Here are some things to watch between now and when the filing period ends on Dec. 11.

Texas House

There could be at least 50 incumbent Republicans facing primary challenges in March. It's part of the ongoing struggle within the party between establishment Republicans and hard-right conservatives.

Texas House Speaker Joe Straus' announcement that he's retiring when his term ends next year has spiced what could already be intense and costly legislative races. He has $10 million in his campaign fund to spend on candidates and incumbents he likes.

Meanwhile, activist groups backed by Midland oilman Tim Dunn are also expected to remain heavily involved in legislative races.

Texas Senate

North Texas is the staging ground for several hotly contested state Senate races.

In Collin County, educator Angela Paxton of McKinney is vying for the Senate District 8 seat against Dallas County Republican Party Chairman Phillip Huffines of Richardson. Paxton is the wife of Attorney General Ken Paxton, while Huffines is the twin brother of Texas Sen. Don Huffines.

The race could split loyalties, as both are viewed as extremely conservative. The seat is open because incumbent Sen. Van Taylor is seeking to replace retiring U.S. Rep. Sam Johnson.

Watch to see if another viable candidates enters that race.

Meanwhile, state Rep. Cindy Burkett, R-Sunnyvale, is challenging incumbent Bob Hall of Edgewood for the District 2 seat in the state Senate.

Hall is being supported by Lt. Gov. Dan Patrick. Burkett's considerable support includes Republican Bob Deuell, whom Hall beat in the 2014 GOP primary.

And in Senate District 30, state Rep. Pat Fallon of Frisco is challenging Wichita Falls incumbent Craig Estes. Another candidate could join that primary race.

Congress

The retirement of Jeb Hensarling of Dallas will result in a new lawmaker representing the 5th Congressional District. Former state Rep. Kenneth Sheets of Dallas has already announced his candidacy. Others considering campaigns in the Republican primary include former Florida Rep. Allen West, who now lives in North Texas, and Reps. Dan Flynn of Van and Lance Gooden of Terrell.

Democrats are excited about their primary contest for the 32nd Congressional District seat held by Sessions, R-Dallas, chairman of the powerful House rules committee.

Contenders expected to officially file candidacies included Dallas lawyer and former NFL player Colin Allred, former Hillary Clinton adviser and Barack Obama appointee Ed Meier, former Obama appointee Lillian Salerno and Dallas lawyer George Rodriguez.

In the GOP primary to replace Johnson in the 3rd Congressional District, Taylor is expected to cruise to the GOP nomination.

Dallas County district attorney

Republicans appear to be rallying around incumbent Faith Johnson, who has been aggressively campaigning to keep the seat. Earlier this year, Abbott appointed Johnson to replace Susan Hawk, who resigned to focus on her health.

Democrats are eager to retake the seat, and two candidates, former state District Judges John Creuzot and Elizabeth Frizell, are vying for the party's nomination.

The big question: Will former District Attorney Craig Watkins try to make a comeback and join the Democratic primary race?