The broad presumption in Washington is that Donald Trump’s quasi candidacy will be a disaster for Republicans.

Part of this Trump talk is merely Democratic hope in the guise of analysis. It fits their narrative that the GOP field is so impossibly weak that even he can lead the pack. What could President Obama have to fear from such a bunch?

Another part of the conventional wisdom is the assumption that anything as weird as the Trump infatuation has to be bad for the party involved. If a politically minded celebrity – say Jon Stewart – had been competitive in early Democratic polls for 2008, it would not have been deemed a good sign for the party. What is unfamiliar is usually deemed bad by the political establishment.

But it is instead President Obama and the Democrats who have more to be concerned about in the spring fever for the boom-and-bust billionaire.

Certainly the reality host with the cantilevered coiffure could cost Republicans the presidency in 2012 if he is serious about running. If Trump goes all-in, develops a core following in the Republican primaries and then runs a well-funded spoiler campaign as an independent in the general election it could make the difference in a swing state or two.

The more likely scenario is one in which Trump does not invest a billion dollars in a third-party run and instead, having hyped the finale of his reality to show to high heaven, returns to the political sidelines. Even if Trump decides to wade into the Republican nominating process, there is considerable doubt that he could muster a huge following.

As more on his past positions trickles out -- including a call for Canadian-style government health care and a 14.25 percent one-time tax assessment on multi-millionaires – the current fascination among small-government conservatives will fade.

However Trump exits the political stage, he will have certainly have left his mark on the Republican cast and the plotline of the 2012 drama. It is the shape of these changes about which Obama and the Democrats should be concerned.

Trump has offered his fellow Republicans a clinic in how to get attention and speak bluntly. American voters are desperate for some straight talk. Trump’s positions may change, but his efficacy in delivering them is constant. He knows how to get his point across and take the fight to Obama, something the other presidential pretenders have been unable to do.

Some of Trump’s popularity stems from the same place as that of New Jersey Gov. Chris Christie. American politics has turned into a foamy sea of blather on which politicians constantly tack and jib. Trump, like Christie, speaks in plain English and doesn’t always seem to be hiding something the way everyone else does.

The Republicans are getting hip to the new style. Listen to Former Minnesota Gov. Tim Pawlenty and Mississippi Gov. Haley Barbour on the stump. They are hitting harder and hedging less. They can thank The Donald for the instruction.

Then there’s the “birther” thing. Democrats suggest that the reason for Trump’s success is that Republicans have gone batty over claims that Obama was not born in Hawaii as he says. Trump is the only potential 2012 contender that has embraced – vigorously – this line of inquiry.

The suggestion from Democratic pollsters is that Trump has succeeded by bringing Obama’s origins into the Republican discussion, and that other candidates will eventually be pressured into taking up his skeptical stance. Democrats see a “birther” litmus test forming for the GOP field, a test that, once passed, will prove a disqualification in the general election.

Why do you think that it is liberals who spend more time talking about the president’s birth than conservatives? The left believes that Republicans will be drawn into this conspiracy theory and that regular Americans will be shocked when the eventual nominee is unmasked as a kook by the mainstream press later on.

But that strategy depends on a long conversation about the president’s origins, which is not a helpful topic for the incumbent. It is because Democrats are constantly pointing to Trump’s allegations that the birthplace question has gone mainstream.

A FOX News poll shows that while only a quarter of American voters think Obama was not born in the United States, 41 percent think that it’s a legitimate line of inquiry. That’s not a number that you want to see as an incumbent president. If that many Americans think that it’s fair to ask if you have pulled off a constitutional swindle of epic proportions it does not suggest deep trust and connection with the electorate.

While 37 percent of Republicans believe Obama was born elsewhere, 12 percent of Democrats and 21 percent of independents don’t believe in his Hawaiian nativity either. The doubts may be deeper on the Red Team, but the concept is certainly part of the national discussion.

Trump has also posed the question in the fashion most damaging to Obama. Trump is not saying he knows that Obama was born anywhere else, but instead has focused on the existence of Obama’s birth certificate. The president has issued a copy of his certificate of live birth provided by public health officials, but Trump wants to know why Obama has never shown his original, signed birth certificate.

The White House has long maintained that this refusal stems from a desire not to dignify unworthy inquiries. As former press helmsman Robert Gibbs said, “nothing would satisfy” the conspiracy theorists, so Obama has decided to ignore their bleating. But as questions grow and Trump restates his demand over and over again, the Obama campaign’s argument that showing the certificate is beneath the president might wear thin.

What then? Does the president cave in and release the document under pressure from a reality show host? Does he let the doubts linger?

Trump’s “birtherism” may be a hidden trap for Republicans, but for a president who learned last summer from a Pew poll that 18 percent of Americans thought he was a Muslim and 43 percent weren’t sure what his faith was, it’s an obvious problem.

It’s just not a helpful line of discussion for a guy who struggles so much to connect with ordinary American voters.

Chris Stirewalt is FOX News’ digital politics editor. His political note, Power Play, is available every weekday morning at FOXNEWS.COM.