At least four lawmakers will have their careers end this month, as August could prove the toughest stretch in a rough year for House incumbents.

More than a dozen members are facing difficult contests in the next few weeks, many of them against fellow lawmakers.

Congress remains immensely unpopular, but most of these races have nothing to do with unhappy voters and a lot more to do with the once-a-decade redistricting process. It has scrambled many district lines, forced incumbents to run against each other and undercut the powers of incumbency, since many lawmakers are running in districts where voters don’t know them.

“This is a tough time mostly because of redistricting, not because of an anti-incumbent bias,” said Cook Political Report House editor David Wasserman. “We’ve got a lot to watch this month.”

August features four races between incumbents where one won’t be coming back. Reps. Lacy Clay (D-Mo.) and Russ Carnahan (D-Mo.) will face off on Aug. 7, as will Reps. Gary Peters (D-Mich.) and Hansen Clarke (D-Mich.).

Next up are Reps. John Mica (R-Fla.) and Sandy Adams (R-Fla.) on Aug. 14, followed by Reps. David SchweikertDavid SchweikertMembers of Congress demand new federal gender pay audit Republican candidate favored in Arizona special House election Ryan leaves legacy of tax cuts and deficits MORE (R-Ariz.) and Ben Quayle (R-Ariz.) on Aug. 28.

Other incumbents who face competitive August primaries are Reps. John Conyers Jr. (D-Mich.), Paul GosarPaul Anthony GosarOvernight Energy: Spending bill targets Pruitt | Ryan not paying 'close attention' to Pruitt controversies | Yellowstone park chief learned of dismissal through press release GOP offshore drilling proposal triggers debate Republican moves on Arizona coal plant show they don’t believe their own rhetoric MORE (R-Ariz.), Chuck FleischmannCharles (Chuck) Joseph FleischmannDems best GOP as Scalise returns for annual charity baseball game Sadly, fiscal restraint is no longer a core principle of the GOP GOP could punt funding fight to January MORE (R-Tenn.) and Diane BlackDiane Lynn BlackScalise throws support behind Black, Blackburn ahead of Tennessee primary GOP lawmaker: Porn partly to blame for school shootings GOP lawmaker introduces bill to crowdfund border wall MORE (R-Tenn.).

Meanwhile, Rep. Todd Akin (R-Mo.) is the underdog in his three-way Senate primary. Rep. Jeff FlakeJeffrey (Jeff) Lane FlakeSenate chaplain offers prayer 'as children are being separated from their parents' Romney backs Laura Bush on border: 'We need a more compassionate answer' Mark Sanford’s troubles did not begin with Trump MORE (R-Ariz.) remains the heavy favorite in his Senate primary, but his opponent has been spending heavily against him.

Here’s a breakdown of the upcoming races:

Clarke vs. Peters (Aug. 7)

Peters had his swing district dismantled by a GOP-drawn map, and decided to run in a heavily Democratic district that encompasses about half of Detroit as well as a good chunk of his old suburban territory.

While Peters is white and Clarke is half-African-American, half-Indian-American, most of the city’s African-American political establishment as well as many of the powerful local unions have lined up behind Peters. Clarke, meanwhile, has run a less-than-stellar campaign. Peters appears to be the strong favorite in the race.

Clay vs. Carnahan (Aug. 7)

Carnahan decided to run against Clay after a GOP-drawn redistricting map backed by some of Clay’s statehouse allies eliminated Carnahan’s district. The two scions of powerful Missouri Democratic dynasties are less than best friends — Carnahan lost his temper and swore at Clay on the House floor during the testy redistricting process — and this race has shown some sparks on both sides.

Clay is the heavy favorite in the race. Most of the St. Louis district is territory he’s previously represented, and he has a much more liberal voting record than Carnahan, who represents a GOP-leaning district in the city’s suburbs. Clay is also African-American, like most of his constituents, while Carnahan is white.

Adams vs. Mica (Aug. 14)

Mica, the powerful House Transportation Committee chairman, is facing Adams, who has run as a Tea Partier in this race. 

The district contains a bit more of Adams’s territory than Mica’s, but Mica remains better-known locally after years in office and has a big cash advantage. Adams has attacked him for earmarks and has a path to victory, but Mica remains the favorite.

Schweikert vs. Quayle 

(Aug. 28)

Quayle represents more of the newly drawn district than Schweikert and has the backing of a number of prominent politicians, including retiring Sen. Jon Kyl (R-Ariz.). But Quayle barely won his 2010 primary and is regarded as a favorite of House leadership, a less-than-advantageous position. Schweikert is the candidate with less establishment ties, has long been on the ballot in the district as a state lawmaker and has more grassroots support.

Schweikert and a group backing him have both circulated polls showing him with a double-digit lead. Quayle disputes that, but he hasn’t released his own polling to prove it. Schweikert has the edge in this race.

Fleischmann (Aug. 2)

 The freshman lawmaker is facing a spirited challenge from Weston Wamp, the son of former Rep. Zach Wamp (R-Tenn.), as well as from businessman Scottie Mayfield (R).

Fleischmann barely won his 2010 primary, Wamp is well-known locally and Mayfield has been spending heavily on the race, though observers say he’s run an imperfect campaign. This could be a close finish.

Black (Aug. 2)

The freshman congresswoman won her primary two years ago against local Rutherford County GOP Chairwoman Lou Ann Zelenik by just 287 votes, and Zelenik is running again.

While a local businessman has poured hundreds of thousands of dollars into the race on Zelenik’s behalf because of their shared concern that Islamic Shariah law will be imposed on the United States, as well as their opposition to the construction of a nearby mosque, her political base of Rutherford County was removed by lawmakers looking to shore up Black in redistricting. Black is likely to win the race.

Conyers (Aug. 7)

The House Judiciary Committee ranking member, 48-year incumbent and civil rights icon is a fixture in Detroit, but his district was greatly altered in redistricting to take in more suburban territory and includes parts of the city he hasn’t represented — more than half the district is new to him.

Conyers is facing three credible challengers in the race, and local observers say he hasn’t worked very hard to assure himself of a victory. Still, he’s raised more money and remains the best-known candidate in the district, and none of his opponents have emerged as the clear alternative. He’s favored to win reelection.

Gosar (Aug. 28)

The freshman lawmaker is running in a district that is mostly new to him. He faces a tough challenge from Arizona state Sen. Ron Gould (R), who has the backing of the big-spending, fiscally conservative Club for Growth.

The group has already spent $120,000 against Gosar in recent days and could increase that going forward, putting a major target on his back in the staunchly conservative district.

Akin (Aug. 7)

The six-term lawmaker has struggled with fundraising and is third in recent polls in his Senate race against former Missouri Treasurer Sarah Steelman (R) and businessman John Brunner.

Flake (Aug. 28)

The Tea Party hero is the clear favorite in the race, but businessman Wil Cardon (R) has spent millions of his own money, forcing Flake to respond. Retiring Sen. Jon Kyl (R-Ariz.) and Sen. John McCainJohn Sidney McCainTrump plan to claw back billion in spending in peril McCain calls on Trump to rescind family separation policy: It's 'an affront to the decency of the American people' Senate passes 6B defense bill MORE (R-Ariz.) endorsed Flake — seen as a sign the party is concerned — but the House member is favored to win.