"I will leave the U.S. Congress when the term for which I was elected expires in January 2011 and return to the practice of law with a sense of duty fulfilled," Diaz-Balart said during a press conference at Florida International University Thursday afternoon. "And with profound gratitude to Cristina and my sons, to my mother, my three brothers and the rest of my family, to Ana Carbonell and all my wonderful staff, to my friends, supporters and my constituents, for having allowed me the honor of service by way of this important public office."

Rep. Mario Diaz-Balart (R-Fla.) confirmed Thursday he plans to run for his brother's seat.

"This is a natural move for me," he said in a statement. "In my years of public service at both the federal and state levels, I have had the privilege of representing most of the communities that make up Congressional District 21, including Hialeah, Westchester, Doral, Kendall, Miami Lakes, Hialeah Gardens, Medley and Palmetto Bay. I have done so with devotion and dedication, effectively and with proven results."

Lincoln Diaz-Balart has publicly toyed with the idea of leaving the House of Representatives, and was even thought to be a potential Senate appointee last year when Sen. Mel Martinez (R-Fla.) resigned.


Mario Diaz-Balart, who won in 2008 by a 53-47 margin, is switching to a more Republican district, but he leaves behind an open seat that could be more susceptible to takeover than his older brother's.

After the 2010 census, redistricting is expected to add a seat in the South Florida area next cycle. With younger generations of Cuban-Americans more open to voting for Democrats, the majority party has set its sights on taking some seats in the area.

Both Diaz-Balart brothers had well-funded challengers in 2008, with Lincoln Diaz-Balart having an easier time with former Hialeah Mayor Raul Martinez. While his brother edged Democratic consultant Joe GarciaJoe Antonio GarciaFormer Florida congressman fined 6K in campaign finance scheme Overnight Defense: Biden honors McCain at Phoenix memorial service | US considers sending captured ISIS fighters to Gitmo and Iraq | Senators press Trump on ending Yemen civil war Biden pays tribute to McCain at emotional memorial service MORE by six points, Lincoln won 58-42.

His district went only slightly more for Sen. John McCainJohn Sidney McCainMeghan McCain to produce 'Don't Sweat the Small Stuff' Lifetime movie starring Heather Locklear An August ultimatum: No recess until redistricting reform is done Meghan McCain on Pelosi, McCarthy fight: 'I think they're all bad' MORE (R-Ariz.), though — 51-49 versus 50-49 for Mario Diaz-Balart's more rural distirct.

State Rep. David Rivera (R), who is currently running for state Senate, is considered the front-runner for the GOP nod in the 25th district. Other names being mentioned include state Rep. Anitere Flores (R) — also a state Senate candidate — and state Rep. Marcelo Llorente (R). Miami-Dade County Mayor Carlos Alvarez (R) is also being mentioned as a possible candidate.

Meanwhile, State Senate Majority Leader Alex Diaz de la Portilla (R) is edging toward a run, according to a source. "I will make my final decision soon after thoughtful and deliberate consideration," he said in a statement Thursday.

GOPers expect a crowded primary.

“There's no shortage of state senators, state reps., county commissioners who would take the chance in a wide-open primary,” a GOP source said. 

On the Democratic side, Garcia, now an appointee at the Dept. of Energy, is considered a strong candidate.

— This post was updated at 12:41 p.m.