Updated at 5:30 p.m. with comments from Smith and others.

WASHINGTON -- San Antonio Rep. Lamar Smith, an immigration hardliner and climate change skeptic, announced Thursday that he will leave Congress at the end of his current term. He's the second GOP chairman this week from Texas to retire.

He chairs the House Science, Space and Technology Committee. Under GOP rules both he and Dallas Rep. Jeb Hensarling would hit a six-year term limit for chairmen at the end of 2018. Democrats are also hoping to win control of the House, though prospects for that are uncertain a year before the elections.

“I love my job,” Smith said. "If I were able to continue as chairman of the science committee... I would be running for reelection."

Hensarling, who chairs the Financial Services Committee, which oversees the banking industry, announced his retirement on Tuesday. Like Smith, he'll remain in Congress but won't seek reelection next year.

Smith has spent 31 years in Congress, with stints chairing the ethics and judiciary committees. He conceded that partisanship is high but said he's not troubled by the dysfunction in Washington and isn't leaving because of that.

"The atmosphere is what you make of it," he said, adding that patience is helpful in Congress. "Persistence is sometimes more important than IQ."

"Sometimes I think legislators should better be called bakers because we trade in half-loaves and slices and even crumbs," he said. "You're never going to throw a touchdown pass, you're never going to hit a grand slam. You're just going to grind out singles and first downs, but over time, that can add up."

Smith's determined stance on climate policy and immigration have left opponents exasperated, even if they found his gentle manner appealing.

"We need to be having serious discussions in this country on energy policy and the environment and sadly it's just not happening in D.C. That committee really sorts of exemplifies that," said Fort Worth Rep. Marc Veasey, a Democrat on the science committee.

He called Smith "blunt" but also noted that he's often invited fellow Texans to bipartisan dinners. "I've really enjoyed getting to know Lamar," Veasey said. "He is just a real gentleman."

High turnover

Turnover in the 36-member Texas delegation in the U.S. House is unusually high.

Smith is the fourth lawmaker to give up a seat in 2018. GOP Rep. Sam Johnson of Plano, who turned 87 last month, is retiring. Rep. Beto O'Rourke, an El Paso Democrat, is giving up his seat to challenge Sen. Ted Cruz.

Texans chair seven House committees, though only three will hit a term limit next year. The third is Austin Rep. Michael McCaul, chairman of the Homeland Security Committee; he reiterated Thursday that he is seeking reelection.

"You're going to lose a lot of experience and a lot of clout, and we always hate that," said Rep. Randy Weber, R-Friendswood.

Smith turns 70 later this month. He was elected to the House in 1986 after serving in the Legislature and as a Bexar County commissioner.

Over the years, he said in a letter to constituents, "I've been able to shape policy involving ethics, immigration, crime, intellectual property, space, energy, the environment, the budget and high tech."

"This seems like a good time to pass on the privilege of representing the 21st District to someone else," he wrote. "I have one new grandchild and a second arriving soon!! And I hope to find other ways to stay involved in politics. With over a year remaining in my term, there is still much to do. There is legislation to enact, dozens of hearings to hold, and hundreds of votes to cast."

Houston Rep. Sheila Jackson Lee, a Democrat who has served with Smith on several committees and shares Yale as an alma mater -- he also has a law degree from Southern Methodist University -- noted that they've disagreed vigorously on immigration and many other topics.

But she said, "He loves this institution. He is committed to his values" and "he has represented his district ... He's truly a Texas gentleman."

Weber called him "one of the nicest, most civil, fair-minded guys you'd want to meet... He's always kind and cordial to the other side of the aisle, even when they're not so cordial to him."

As science chairman, Smith has pressured climate scientists and tangled frequently with Dallas Rep. Eddie Bernice Johnson, the panel's senior Democrat. Environmentalists aren't likely to miss him.

"It's no secret that the chairman and I don't always agree, but I wish Chairman Smith the best in his retirement," Johnson said in a statement, adding that she has a strong favorite for Smith's successor as chairman: herself.

That would require Democrats to win back the majority -- an outcome Republicans view with as much skepticism as Smith applies to the idea of human-caused climate change.

Climate views

In 2014, Smith joined other Republicans in rejecting a climate report from the Obama administration, calling it "a political document intended to frighten Americans into believing that any abnormal weather we experience is the direct result of human CO2 emissions. In reality, there is little science to support any connection between climate change and more frequent or extreme storms."

The filing period for the March primary opens on Nov. 11, setting off a scramble in Smith's district, which runs from San Antonio to Austin, including New Braunfels and much of the Hill Country, including Kerrville and Fredericksburg.

But the district is likely to remain in GOP hands. President Donald Trump beat Democrat Hillary Clinton 52-42 there, and Smith won last year with 57 percent of the vote -- the worst showing of his congressional career but still a landslide 21-point margin over his Democratic challenger.

"I told him today -- you're going out on top," said Rep. Roger Williams, an Austin Republican. "There's a lot of athletes, a lot of politicians, a lot of business guys who don't know when to do that."

Rep. Michael Burgess, R-Pilot Point, called it a blow for Texas to lose two chairmen. That, he said, "means the rest of us have to work harder, and we will."

Even as he pushed his science agenda Smith has remained deeply engaged on immigration policy, demanding tougher security at the border and more aggressive interior enforcement. Unlike some Republicans, he hasn't been shy about praising Trump.

"The president deserves a lot more credit than he's getting," Smith said, citing growing consumer confidence and a roaring stock market. "There's a lot right about the way the country's going and I think the president deserves a lot of that credit."

Dallas Rep. Pete Sessions, whose chairmanship of the House Rules Committee is not term-limited -- the speaker controls that post directly -- said both Hensarling and Smith "have done an awesome job."

Possible GOP setbacks?

Democrats cited Smith's retirement as a sign of looming setbacks for the GOP majority in the 2018 elections, though they made no boasts about this particular district. Historically, the president's party suffers significantly two years after his election, and Trump's approval ratings are unusually low.

"From Texas to Pennsylvania and Washington, House Republicans are dropping like flies because it's nothing short of miserable to be part of Speaker Ryan's establishment Congress," said Meredith Kelly, communications director at the Democrats' House campaign arm. "These retiring Republicans have seen the writing on the wall, and they're not waiting around for the midterms."

GOP strategists aren't worried about keeping control of the district.

Smith himself expressed confidence that a fellow Republican will succeed him. He vowed to serve out the remaining 14 months of his term and said he hasn't considered yet what he'll do next.

Rep. Ted Poe, R-Humble, called Smith "a great representative.... He gives the Texas delegation dignity." Given the number of times courts and the legislature have redrawn the state's political map, he quipped, "he's represented almost all of Texas because of redistricting."

Washington correspondents Nicole Cobler and Caroline Kelly contributed to this report.