Republican presidential candidate Donald Trump. (AP Photo/Isaac Brekken)

Several House and Senate Republicans are facing stiff challenges on Super Tuesday from primary opponents who are tapping into the anti-establishment fervor stoked by Donald Trump’s run for the White House.

Trump has inspired record turnouts in each of the four GOP nominating contests so far this year, leaving some incumbents who have previously enjoyed easy re-election contests worried his supporters will vote to kick them out when they show up to cast their ballots for the business mogul.

“You have people turning out to support a guy like Donald Trump who is talking about blowing up the system,” said Lisa Boothe, a former House GOP aide, campaign strategist and founder of High Noon Strategies.

This tension is on display in hotly-contested southern states like Alabama and Texas, where several veteran lawmakers are scrambling to make sure the Trump wave doesn’t wash their political careers out to sea.

Lawmakers holding some of the most powerful seats in Congress – such as House Ways and Means Chairman Kevin Brady (R-Texas), House Rules Committee Chairman Pete Sessions (R-Texas) and Senate Banking Committee Chairman Richard Shelby (R-Ala.) – are among those in tight races. Also on the list are freshman conservative Rep. Bradley Byrne (R-Ala.) and Rep. Martha Roby (R-Ala.).

For most of these lawmakers the concern isn’t that they will lose outright on Tuesday, but that they will fail to register enough support. Texas and Alabama both have two-step primary elections where candidates must receive more than 50 percent of the vote in order to avoid a run-off.

While veteran Republican lawmakers have come to fear primary challenges more in recent years following the rise of the tea party, campaign strategists said the concern is particularly acute this year as the anti-establishment climate is inspiring voters who would normally stay home to come out and vote in the year of Trump.

The security blanket once provided to incumbents by broad name recognition and financial help from party backers is fraying, leaving lawmakers to wrestle with how much to embrace their congressional experience while seeking to assure restless primary voters that they share their anger over the status quo.

“My general advice to incumbents is don’t be scared,” said GOP strategist and former National Republican Congressional Committee deputy political director Brian O. Walsh. “Be prepared and go run the campaign you need to run.”

Walsh said that the biggest mistake incumbents make is not taking their primary challengers seriously. Many strategists point to former House Majority Leader Eric Cantor (R-Va.), who lost his seat in 2014 to a shockingly strong primary challenge from tea party favorite David Brat. A similar story played out in 2010 when Mike Lee ousted Robert F. Bennett (R-Utah) who had been in the Senate since 1993.

Brady and Sessions have been forced to spend significant time and money to fight challengers who might get little attention in previous years.

What follows is a look at some of Tuesday’s top races, all of them Republican primaries.

Rep. Kevin Brady, Texas’ 8th Congressional district

Brady, a former Texas Chamber of Commerce official, was first elected in 1997 and chairs the House’s tax writing committee. He faces three challengers — Steve Toth, Craig McMichael and Andre Dean — all of whom are attacking his record as insufficiently conservative. Toth is backed by several tea party-affiliated groups and has aggressively gone after Brady as being part of the Washington establishment.

Trump voters are not Brady’s only threat. Texas Sen. Ted Cruz, who has attracted a separate strain of anti-establishment voters, is very popular in the district.

Rep. Pete Sessions, Texas’ 32nd Congressional district

Sessions, a former district marketing manager for Southwestern Bell, was first elected in 1996 and chairs the House Rules Committee. He previously served as chairman of the National Republican Congressional Committee.

Like Brady, Sessions faces three challengers — Paul Brown, Russ Ramsland and Cherie Myint Roughneen. Ramsland, an oil and gas executive, is the most vocal and well-funded of the challengers and has accused Sessions of becoming increasingly moderate during his time in Congress. Ramsland recently released a mailer attacking Sessions for his slipping rating among Washington-based conservative groups like the Club for Growth. Sessions has a 84 percent lifetime rating from the group, down from 91 percent in 2010.

Richard Shelby, senior senator from Alabama

Shelby was first elected to the Senate in 1986 and chairs the Banking Committee. He previously chaired the Senate Intelligence Committee and represented Alabama’s 7th congressional district from 1979 to 1987. Shelby is facing four challengers: Jonathan McConnell, Marcus Browman, John Martin and Shadrack McGill.

McConnell, considered Shelby’s strongest competitor, is 33 and a relative unknown in the state. He’s attacked Shelby for his “big spending ways.” Shelby is backed by the NRA, the Tea Party Patriots Citizens Fund, National Right to Life and many other groups. He is also backed by fellow Alabama Republican Sen. Jeff Sessions, who recently announced his endorsement of Trump.

Rep. Martha Roby, Alabama’s 2nd Congressional district

Roby is an attorney and a former member of the Montgomery City Council. She was elected in 2010 after being endorsed by several prominent Republicans, including Sarah Palin and Newt Gingrich. Roby faces two challengers, local tea party founder Becky Gerritson and Bob Rogers. Gerritson is considered the most serious challenge.

Roby has a significant fundraising and spending edge over all of her competitors. She outspent Gerritson by over $50,000 between October and December, according to campaign filings with the Federal Election Commission. Roby has endorsements from the National Rifle Association and the Chamber of Commerce.

Rep. Bradley Byrne, Alabama’s 1st Congressional district.

Byrne was elected in a special election in 2013 and is facing a rematch against Dean Young, whom he narrowly defeated in a runoff that year. Young has attacked Byrne for not being sufficiently conservative. Byrne has been endorsed by the NRA and National Right to Life.