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NORTH TEXAS (CBSDFW.COM/AP) – Two long-time North Texas representatives in Congress face opposition at the polls. The 30th and 32nd congressional districts cover large sections of Dallas County.

In the 30th congressional district, Eddie Bernice Johnson is running for re-election. She’s held her seat in the House of Representatives since 1993.

Johnson faces off against Barbara Mallory Caraway on the Democratic ticket. Caraway is the wife of former Dallas city councilman and current County Commissioner candidate Dwaine Caraway.

In the 32nd congressional district, Republican Pete Sessions wants to keep his position. He has represented northeast Dallas County in the U.S. House since 2002.

Sessions faces opposition from three Tea Party candidates this year – Paul Brown, Russ Ramsland, and Cherie Myint Roughneen.

House Ways and Committee Chairman Kevin Brady, who was elevated to the powerful post last fall, faces three conservative challengers in arguably the biggest fight of his 10-term career. Former state legislator Steve Toth is among his opponents, and with Republican voters railing against establishment candidates this election year, Brady may be thrown into a May runoff to defend his suburban Houston district.

Another longtime congressional fixture form Houston, Democrat Gene Green, also is facing a potentially stiff primary challenge from former Harris County Sheriff Adrian Garcia. The district is about 60 percent Hispanic, but top national Hispanic groups have backed Green.

The opening of a South Texas seat is also renewing the potential for the state to send its first Hispanic woman to Congress. Dolly Elizondo has the backing of former gubernatorial candidate Wendy Davis and U.S. Sen. Kristen Gillibrand, the New York Democrat, in a crowded race to replace retiring U.S. Rep. Reuben Hinojosa. A runoff appears likely for the district that runs from San Antonio to the border.

A second round of primary voting also seems likely in the West Texas district where U.S. Rep. Randy Neugebauer is retiring and hasn’t endorsed any of the nine Republican candidates running to replace him.

Across the state, Republican House Speaker Joe Straus, who is on the verge of a record-tying fifth session as Texas speaker, is again the main target of conservative activists who accuse him of being cozy with Democrats and derailing get-tough immigration proposals.

Megadonors including Alice Walton, heiress to the Wal-Mart fortune, have written big checks to businessman Jeff Judson in a brash campaign against Straus. His attacks against the speaker included claims that because Straus is Jewish, he doesn’t connect with Christian conservative voters. The even-tempered Straus has seldom fired back but has been forced to spend money to defend his record and his San Antonio district.

Straus, a friend of the Bush family whose supporters include Texas’ elite donor class, has kept his powerful post in recent years despite the Legislature pushing farther to the right. His political durability this cycle will be a test in an election year where anti-incumbent anger has been strong among Republican primary voters elsewhere.

Find out what you need to know about voting on the Dallas County Elections webpage, just click on “Election Day Information.”

Transportation to the polls is also being made easier. Passengers who show a valid voters registration card can ride DART free today, between the hours of 6 a.m. and 8 p.m.

Polls are open from 7 a.m. to 7 p.m.

(©2016 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)