The former head of a Republican consulting group has pleaded guilty to jamming Democratic telephone lines in several New Hampshire cities on Election Day two years ago.

The jamming involved more than 800 computer-generated calls and lasted for about 1 1/2 hours on Nov. 5, 2002, the day voters decided several races, including a close Senate contest between outgoing Gov. Jeanne Shaheen and GOP Rep. John E. Sununu, who won by fewer than 20,000 votes.

The lines that were jammed were set up so voters could call for rides to the polls. Democrats say the jamming was an organized, statewide effort that may have even affected the outcome of some local races.

Allen Raymond, former president of the Virginia-based GOP Marketplace, pleaded guilty Wednesday in federal court to conspiring to make harassing phone calls. The charge carries up to five years in prison. He will be sentenced in November.

The Justice Department said the investigation continues.