Republican Rep. Paul Ryan, a leading House advocate of immigration reform, sounded decidedly cautious when asked on ABC Sunday whether Congress can pass a reform bill to send to the president this year. "I really don't know the answer to that question," Ryan said. "That is clearly in doubt."

That certainly appears to be true — after all, a large number of House Republicans oppose some significant parts of the GOP immigration reform principles unveiled at the party's retreat last week. So there is plenty of reason to take Ryan's statement as a plainly factual assessment of the situation.

But Ryan's words still set off suspicions among opponents of immigration reform. They've heard such pessimistic talk from reform advocates before and believe it has been an effective rhetorical tool for supporters of Gang of Eight-style reform.

In this way: If the public hears constantly that immigration reform is in trouble on Capitol Hill, that it has little or no chance of passage, then conservative activists, reassured that there's no threat, aren't likely to mobilize against it. What's the need? It's going to fail anyway. But if the public hears that immigration reform is steaming ahead, that the House leadership is determined to pass a bill, or bills, that will end up in conference with the Senate's already-passed Gang of Eight comprehensive immigration reform measure -- if the GOP base hears that, it will recognize the risk, speak out, and at the very least make things more difficult for immigration reform advocates.

So better to talk down the chances of the reform's success. "The best way to pass a bill is to tell people a bill is unlikely to pass," says one Hill aide closely involved in the issue. "What if Ryan had gone on TV and said, 'Read my lips, we're going to pass a bill'? Can you imagine how much more difficult it would be is for Republicans when they go home to town halls?"

The aide recalls how Senate GOP Gang of Eight leader Marco Rubio often stressed the downside of his bill's chances. Recalling a closed-door meeting in which Rubio discussed the bill with skeptical colleagues, the aide remembers, "Rubio said, 'Look, there's no way the bill will pass as it is right now. The Democrats are going to lose about five of their own, and it just won't pass.' Rubio would go on Hannity and say the same thing -- Oh, we've got so much work to do, we don't have the votes."

One result of that kind of talk was that conservatives who opposed reform didn't see an active threat until the Gang of Eight bill was on the verge of passage. "The phone lines in Congress didn't melt down until after Corker-Hoeven [the amendment that assured enough Republican support for passage], and everybody realized the countdown had begun," the aide says.

Now, some Hill conservatives — maybe those of a particularly suspicious bent of mind — see something similar beginning. "When Ryan says things like it's going to be tough to pass, I don't see that as meaning Ryan and the $10 billion coalition that is trying to pass the bill is calling things off," says the aide. "I think it's saying to conservatives to leave us alone while we work on it."

The bottom line is that a popular perception that immigration reform is in imminent danger of defeat will tend to motivate those who want to pass it and not motivate those who want to stop it. That is not saying Paul Ryan wasn't giving his best assessment of the bill's chances at the moment. But that assessment also happens to help the cause.