Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a columnist at Newsday since 2007.

Early on, the polling on Donald Trump’s repeated and emphatic call for banning all Muslims from entering the U.S. showed a majority of Republicans in favor and a majority of Democrats against.

So now that he’s all but locked up the GOP nomination and looks to the general election, presto! The tough-talking billionaire tosses up a cloud of doubt around his own signature issue.

Oh no, he now says, he didn’t mean all Muslims — just those from “terrorist” nations. Not like, say, Scotland, where he was visiting when the waffling became clear. As with his Mexican wall, the Muslim “policy” still brings a thousand honest and practical questions.

But there’s no question what he’s up to. This is one blustery candidate’s version of a textbook political retreat.

Carl Paladino, Trump’s leading New York State supporter, told The Wall Street Journal the other day: “Expecting a clear definition is a little bit much in the middle of a presidential campaign.”

Paladino is suggesting here that it may be too much for a certain candidate to tell you what he is talking about and then stick to it.

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Of course, Trump supporters tell you he isn’t a politician — you know, one of those folks who leads you on with vague promises and then backs off when it polls badly.

But this sounds like a clumsier version of Hillary Clinton on trade. She moved from claiming the Trans-Pacific Partnership “sets the gold standard” to opposing it under pressure from rival Bernie Sanders against corporate trade deals that export jobs.

In making this about-face months ago, she gave the rationale that she found the proposed TPP terms “didn’t meet my standards” for jobs and wages.

She said she “absorbed new information.” That new information arrived, it seems, just in time to shed a burdensome position; that is, after backing such deals with Oman, Chile and Singapore while a senator.

Illegal immigration as a whole has stymied gridlocked Washington, D.C., for more than a decade. By all accounts, President Barack Obama’s administration expelled record numbers of those in the U.S. without documents.

But when he unilaterally ordered 5 million people to be protected from deportation, it met with a successful court challenge. This week the U.S. Supreme Court refrained from upholding Obama’s action.

On her website, Clinton vows to “enact comprehensive immigration reform to create a pathway to citizenship, keep families together and enable millions of workers to come out of the shadows.”

All along, Trump has called for a staffed-up deportation force to remove millions here without permission and doubled down on his big wall.

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What either of them could accomplish without congressional authorization is a very relevant matter. But it is hard to predict what 535 federal lawmakers would do under a new president when competing candidates for the White House are still in the process of keeping options open.