How does packing and cracking in gerrymandering create vulnerability for incumbents?
Executive summary
Packing concentrates opposition voters into a few overwhelmingly safe districts so their votes are “wasted,” while cracking spreads them thin across many districts so they can’t form a majority; both techniques reduce electoral competition and can entrench or, paradoxically, expose incumbents to new risks (packing can turn formerly safe colleagues into competitive neighbors) [1] [2] [3].
1. How packing and cracking work in plain political terms
Packing piles like-minded opponents into one or a few districts where they win by huge margins; cracking disperses opponents across multiple districts so they lose everywhere. The practical result is a set of “safe” seats for the party in control of the mapmaker’s pen and a reduction in the number of truly competitive districts [1] [4] [5].
2. Why mapmakers use these tools to protect incumbents — and how that protection is supposed to function
When the party that controls redistricting draws districts, packing and cracking let it convert vote distributions into predictable wins, turning general elections into routine re‑elections for incumbents and shifting real contest to primaries. Parties prefer safe seats because incumbents are easier to reelect and less expensive to defend than creating a slate of vulnerable candidates [6] [7] [3].
3. The vulnerability paradox: how packing can backfire on incumbents
Packing can create a hidden vulnerability: if mapmakers “eliminate” opposition districts by compressing those voters into others, former safe incumbents elsewhere may inherit more rival voters and suddenly face tougher reelection fights. Analysts call this a “backfiring gerrymander” or “dummymander” — removing some opposition seats can make adjacent seats more competitive and imperil incumbents who accepted tradeoffs to help the party overall [8] [9].
4. Cracking’s direct route to incumbent exposure
Cracking dilutes a constituency by slicing it into pieces across several districts. That can split an incumbent’s reliable base, weaken their natural coalition, and create contests where incumbents must cultivate new voters or face loss. Cracking also produces many marginal voters whose shifting turnout or preferences can flip a seat in a wave election, turning previously comfortable incumbents into targets [2] [10].
5. Kidnapping, stacking and other tactics that increase incumbent risk
Redistricters sometimes “kidnap” — move an incumbent’s home into a different district — or “hijack” by forcing two incumbents into the same seat. Packing, cracking, kidnapping and stacking can be used in combination to protect one incumbent at the expense of another, creating intra‑party fights and unexpected incumbent vulnerability [11] [5].
6. Institutional and legal context that shapes risk
Federal courts largely removed themselves from policing purely partisan gerrymanders in Rucho v. Common Cause, leaving state courts and politics to constrain mapmakers; that means parties and incumbents must trade safety among themselves or risk reversals through state‑level litigation over racial gerrymanders and state constitutional limits [12] [9].
7. Quantitative and systemic consequences — why incumbents worry
Packing and cracking create “wasted votes” and reduce the number of competitive districts; in 2025 reporting, analysts found only a small fraction of districts truly competitive, which both entrenches many incumbents and concentrates risk into the relatively few remaining swing seats. When redistricting trades away marginal seats to secure others, incumbents can be collateral damage in those calculations [2] [5] [3].
8. Competing perspectives and hidden motives to watch for
Pro‑reform groups argue packing and cracking destroy accountability and entrench incumbents, while some political strategists defend aggressive maps as a legitimate partisan tool; incumbents themselves may accept vulnerable seats for the “team” benefit of preserving a broader majority. Observers should note that mapmakers often make explicit tradeoffs — protecting senior members or key districts even if it creates new competitive exposures for others [7] [13] [3].
9. What this means for voters and campaign strategy
Where packing or cracking is used, voters lose the regular threat of replacement that disciplines representatives; incumbents placed in newly competitive districts must reorient toward broader electorates, face more recruiting and fundraising pressure, or risk being primaried or defeated. Remedies proposed by reformers — independent maps or proportional systems — would undercut the leverage those tactics give map drawers [7] [13].
Limitations: the sources provided describe the mechanics, political incentives and examples of packing, cracking and related tactics, but available sources do not mention specific, single-seat case studies in 2026–2028 beyond the general examples referenced above; for details on particular incumbents’ vulnerability you will need jurisdictional maps and vote data not included in these excerpts [8] [3].