When the Lone Star State hosts its congressional primaries next week, it will be akin to Thunderdome in contests across the state -- only it's more like a half-dozen candidates enter, and two will leave.

Competitive primaries will take place in a large portion of the state's 36 congressional districts, in part thanks to new open seats created in the decennial redistricting process -- but also with challenges to incumbent members.

Under Texas election laws, unless a candidate captures a majority of the primary vote, the top two vote-getters face off in a July 31 runoff.

With as many as a dozen candidates on a single ballot, observers suggest a slew of primary contests will easily extend into the late summer.

What follows is a breakdown of key Democratic House primaries in Texas. A summary of top Republican races will appear in tomorrow's E&E Daily.

Among the most-watched contests in the state for Democrats is in the San Antonio-area 23rd District, where a trio of Democrats are vying for the right to face freshman Rep. Quico Canseco (R).

"What you've got is a district that was reconfigured, it's still marginally Democratic, but not quite as Democratic as it was before redistricting," said Matt Angle, a veteran Texas Democratic strategist, who heads the Lone Star Project. "The key is to have the strongest campaigner and strongest fundraiser on the Democratic side in the fall to run against a Republican millionaire."

Canseco, who defeated then-Rep. Ciro Rodriguez (D) in 2010 to win his first term, lists his personal wealth at a few million dollars, according to his federal financial disclosure form, although he is not among the richest members of Congress.

Rodriguez is seeking to reclaim his former seat, but he faces competition from veteran state Rep. Pete Gallego and attorney John Bustamante, the son of ex-Rep. Albert Bustamante (D).

Gallego, who has claimed the support of the League of Conservation Voters, has crushed his fellow Democrats on the fundraising front, raising $642,000 as of mid-May, although he banked $83,000 at that time.

Rodriguez raised $95,000 as of mid-May, reporting $61,000 on hand along with a $50,000 debt from loans he made to the campaign.

Bustamante reported raising $28,000 ahead of the primary and had $1,500 on hand at that time, along with a $2,000 debt.

Bustamante is not widely seen as competitive, although his presence on the ballot could prevent Gallego or Rodriguez from claiming a majority of votes.

Angle, who acknowledges he sought to recruit Gallego to run for Congress as early as 1995 during his tenure at the Democratic Congressional Campaign Committee, suggested the state legislator would be the stronger candidate, citing Rodriguez's previous losses in 2004 and 2006 primaries, although he ultimately returned to Congress in a 2006 upset over then-Rep. Henry Bonilla (R), after the Supreme Court changed some House district lines.

Elsewhere in Texas, a trio of Democratic incumbents must also surmount primary challenges in order to compete for their seats in November.

In the San Antonio-based 16th District, Rep. Silvestre Reyes (D) is in a close contest with former El Paso City Councilman Beto O'Rourke (D), as the two lead a five-candidate primary. The winner of a potential Democratic runoff is all but ensured election in November.

O'Rourke has styled himself as a reformer in the race, critical of congressional retention and supportive of term limits. He has become Reyes' most viable challenger since the congressman's 1996 election.

Although he trails Reyes' $1.1 million total in fundraising with $401,000 ahead of the primary, O'Rourke has benefited from a nonpartisan, anti-incumbency super PAC, the Texas-based Campaign for Primary Accountability, which has spent nearly $200,000 opposing Reyes.

Whether that is enough to defeat Reyes remains to be seen.

"People forget Reyes won his first election with someone running from his left when it was an open seat," Angle said. "The question is whether or not he has been able to build enough goodwill in a low-turnout primary."

In the suburban Dallas 30th District, Rep. Eddie Bernice Johnson (D) faces a challenge from attorney Taj Clayton and state Rep. Barbara Mallory Caraway.

Although Caraway can claim a geographic base in the 30th District thanks to her state House seat, she had raised $70,000 as of early May and had $3,000 on hand at that point along with a $7,000 debt.

At the same time, Johnson reported raising $562,000 and retaining $373,000. She reported a debt of $66,000. Although Clayton is the political neophyte of the trio, he has proved himself a successful fundraiser, taking in $402,000 as of early May and keeping $45,000 in the bank.

It remains to be seen whether Mallory Caraway's name recognition in the district as an elected state lawmaker could split the vote enough to force a runoff between Clayton and Johnson.

Rep. Lloyd Doggett (D) likewise faces two challengers in his redrawn Austin-area 35th District seat.

"The Doggett district is a function of redistricting, designed by the people that drew those maps to generate that kind of a conflict between Austin, San Antonio and an Anglo incumbent and a significant Hispanic population," said James Henson, director of the Texas Politics Project at the University of Texas, Austin.

But Doggett faces less of a challenge than he might have when state Rep. Joaquin Castro (D) opted to run in the 20th District, where Rep. Charlie Gonzalez (D) is retiring.

"Nobody could question his record, as a Democrat, his record as a progressive, his environmental record," Angle noted.

Doggett has also built a significant war chest of nearly $2.9 million, raising $1.1 million in the current cycle.

Political observers suggest Bexar County Tax Assessor and former state Rep. Sylvia Romo (D) has run an uninspired campaign against Doggett. She reported raising $26,000 ahead of the primary and retained $20,000 on hand as of early May.

Maria Luisa Alvarado, a former Democratic nominee for lieutenant governor, has also failed to raise significant funds in the race, reporting about $5,000 in mid-May, according to the Federal Election Commission.

Open seats abound

Among the four new congressional seats Texas picked up in the decennial reapportionment process are the Dallas-Fort Worth-area 33rd District and the Brownsville-area 34th District.

Both Democratic-leaning districts have attracted large pools of candidates, all but guaranteeing the races will continue into July.

"After a redistricting cycle, you're bound to see a little bit more of these; that said, there are a lot of races that are awfully hot and contested," Henson noted. "The reasons on each side are a little bit different. On the Democratic side, there's so much pent-up demand ... as a result of Republican dominance of elected office in the state."

Among the top candidates in the 33rd District are state Rep. Marc Veasey, whose state district is almost wholly contained in the new congressional district, and former state Rep. Domingo Garcia (D).

"They're polar opposites in terms of style," Angle said, describing Veasey as a partisan who has focused on building coalitions within his own party, while Garcia is "all sharp edges."

But thanks to his personal wealth, Garcia has bolstered his campaign's ability to spend, loaning his bid $600,000. He raised $127,000 ahead of the primary but reported $241,000 in the bank.

Veasey had raised $301,000 to date and retained $105,000 in early May.

Although businessman David Alameel (D) has managed to put himself on the air, as well, loaning his campaign more than $2.6 million, according to his pre-primary report, Democratic observers in the state suggested he is unlikely to win a spot in the runoff.

Other candidates include former Dally City Councilman Steve Salazar, who had raised $118,000 as of May.

Among the eight candidates vying for the likely runoff in the 34th District seat is Cameron County District Attorney Armando Villalobos -- who faces a serious hurdle in the race after he was indicted earlier this month over allegations he received more than $100,000 in bribes and kickbacks in his current post.

Villalobos has questioned the timing of the indictment and told the Associated Press: "Traditionally, something like that would kill a candidate. But I think the fact that I have two decades of goodwill built into my own community, and people have a track record to go by, and people have seen me in action and seen what I can do; I think that has been a positive for me to get through a period like this."

Villalobos raised $170,000 ahead of the primary and retained about $5,000 on hand.

Another leading fundraiser in the contest is attorney Filemon Vela, who raised $105,000 but also contributed $150,000 in personal loans. He retained $21,000 on hand ahead of the May primary.

But Vela has also faced accusations from local Republicans, who assert he considered seeking the GOP nomination in the race before Texas finalized its new congressional lines.

Other candidates include former Edinburg City Manager Ramiro Garza; Denise Saenz Blanchard, who served as chief of staff to then-Rep. Solomon Ortiz (D-Texas); Salomon Torres, former district director for Rep. Ruben Hinojosa (D-Texas); former Brownsville City Commissioner Anthony Troiani; former Willacy County District Attorney Juan Angel Guerra; and Iraq War veteran Elmo Aycock.