Poll plugging or poll clogging is a voter suppression tactic whereby a group of voters goes to a polling site early and never finishes their voting session, thereby denying the use of the voting machine to other voters. Since many polling places do not have time limits for voting, the group can physically stand at the machines for hours at a time (or generally as long as needed before arising suspicion) and thereby block machine use by other voters in line. If the group has "reinforcement" voters near the front of the line, the recently ejected clogging voters can be replenished and the cycle repeated.

Some states, like Kansas, South Dakota and Ohio have time limits in voting booths, mitigating the effects unless the attack is coordinated with enough "reinforcements" near the beginning of the line.

There have been unsubstantiated rumors that this tactic is planned to be used during election day on November 8th to block Donald Trump voters from being able to use the polling machines.

Poll clogging can be more effective in urban, majority Democrat areas. A small group of dedicated Republican voters who live in such an area and who are assigned to vote at the polling station can arrive earlier than most of the other voters, get on the machines, and hold up the line. Since most voters stuck in line will be Democrat, they will not be able to vote. Examples of vulnerable areas include cities like Philadelphia and Chicago. The affected stations would be powerless to stop a concerted effort by a group of Republican voters at the front of the line, unless strict time limits were instated. Even so, polling could be disrupted/delayed.

The reverse can be applied in rural areas to suppress Republican votes, but since polling centers tend to be more numerous and distributed, it may be less effective.

Another scenario is college campus Republican groups poll plugging campus voting places, since college youth tend to vote Democrat.