As the Senate begins its second week of debate on immigration reform this week, we’ll see whether a “silent majority” on the issue holds sway or whether Washington will be more influenced by the “motivated minority.”

If you have tried to reach your senator during the past two weeks, you probably were put on hold as staff assistants dealt with a barrage of calls about immigration. It’s highly unlikely that the people on the line ahead of you were checking in to tell their senator what a wonderful thing it would be for him or her to support comprehensive immigration reform.

Instead, they were probably hurling invective about what they call “amnesty” provisions contained in the compromise bill that the Senate is now debating. This illustrates an essential truth about politics: A passionate minority often makes more noise on an issue than the majority.

Several polls have come out during the past few weeks demonstrating that the majority of Americans agree that the 12 million illegal immigrants currently in the country should be given a path to legalization—as long as it includes penalties such as fines and requires them to get to the “back of the line” behind those who are trying to immigrate legally.

That is exactly what the Senate bill does. Illegal residents can apply for a “Z visa.” Holders of such a document then have to jump through many hoops, such as waiting about 13 years, paying multiple fines of up to $5,000 and returning home before they become legal.

It’s complicated. When I first saw a White House document earlier this spring outlining the process, I concluded that a path to legalization had been dropped from the compromise bill—and erroneously reported it that way. (I hope my editors don’t actually read this posting.)

But the anti-amnesty crowd, which is composed mostly of conservative Republicans, argues that the fact that illegal residents can indefinitely renew their Z visas without becoming citizens is a form of amnesty. They’re not punished by deportation. In their view, it would be better for the “return home” provision to kick in immediately—a prospect that would roil employers that depend on immigrant labor.

We’ll see soon see how much political capital President Bush wants to spend on combating the amnesty notion. Comments he made on June 1 imply he’s primed for a fight with the right wing of his party.

“If you want to kill a bill, then you just go around America saying this is amnesty,” Bush said. “For those who call it amnesty, they’re just trying to, in my judgment, frighten people about the bill. This bill is not amnesty, but it recognizes that it is impossible for this country to rout people out of society and ‘send them home.’ It’s just not going to happen.”

Perhaps not. But what could happen is that the anti-amnesty sentiment will be so strong that it kills the Senate bill—or a House bill later this summer. There are plenty of land mines available to blow up the legislation, with more than 80 amendments pending in the Senate.

Some of those measures, if they are approved, would upset the delicate Senate compromise that, for now, has conservative Sen. Jon Kyl, R-Arizona, and liberal Sen. Edward Kennedy, D-Massachusetts, on the same page. Significant changes to the bill would cause Kyl and other Republicans to disown it.

One of the advantages that the anti-comprehensive-immigration faction has is that it is skilled in rhetorical jousting. It can make its pitch against the Senate bill in just a line or two. In fact, opponents of the legislation have labeled it with a tidy and prickly sobriquet—“Zamnesty.” The White House, on the other hand, issues four- and five-page fact sheets to rebut the amnesty charge. They’re not nearly as quotable.

So, get ready for a lively and consequential debate in the Senate this week. It could be one of the last tests of President Bush’s political strength. He’s been able to get his way on Iraq funding so far despite approval ratings in the 30s. Now, he’ll be put to the test on immigration.