House Republicans headed into a touchy debate over their own careers are still short dozens of votes in their drive for a constitutional amendment limiting terms in Congress.

Despite and perhaps because of deep divisions within the GOP leadership, House Speaker Newt Gingrich said Monday there would be no arm-twisting in advance of this week's historic vote. Debate began Tuesday afternoon.Supporters of limiting House tenure "are not going to try to muscle" their GOP colleagues, Gingrich said after an appearance in Georgia.

"On constitutional amendments, people have to be allowed to vote their conscience," he said.

The abstinence pledge, however, does not extend to the grass roots. Radio talk shows are filled this week with guests from several term-limits lobbying groups. They are dispensing advice on how to best pressure members of Congress who are resisting the term-limits tide.

Seven in 10 Americans support the idea of capping congressional tenure. Most of them support a three-term, six-year limit for House members, according to a poll released Monday by the National Taxpayers Union.

The House vote, possibly as early as Wednesday, will be on a variety of options ranging from 12 years each in the House and Senate, to six years in the House and 12 years in the Senate.

The most popular proposal will then be subject to a final vote requiring a two-thirds majority - 290 votes - to move on to the Senate and to state legislatures for ratification.

Gingrich said Monday he expected four-fifths of House Republicans, or 184 of them, to support the amendment. By some estimates, only about 25 Democrats were solidly in favor - leaving much ground to make up.

"None of these are expected to pass," said Paul Jacob, executive director of U.S. Term Limits. Furthermore, he said, the three-term limit supported by most Americans "is likely to get the least support in Congress. We want people to know this is a shell game."