He has a real estate empire bearing his name in bright lights. He has had an astonishing influence on the Republican presidential field, making his competitors struggle to appease the right wing of the party while avoiding alienating a less-conservative general electorate. And now Donald Trump, still leading in both national and some state polls for the Republican nomination for president, is bringing his glitzy political brand to Congress.

True, there's no massive "Trump" sign attached to the scaffolding around the U.S. Capitol, or even the Republican caucus rooms inside. But the unexpected success of the bombastic businessman has emboldened the anti-establishment elements on Capitol Hill, experts and lawmakers say. The influence of the ultimate outsider candidate threatens to cause a great deal of internal problems, as Congress faces looming deadlines and battles on federal spending, the highway trust fund, the debt ceiling and the nuclear agreement with Iran. At a time when the GOP-run Congress is desperately trying to prove to voters it can govern, Trump's road show of disruption is encouraging rank-and-file voters as well as some lawmakers to refuse to compromise on major issues – a tactic that could result in another federal government shutdown at the end of the month.

"Trump is fanning the flames. He's already said he'd shut down the government rather than fund Planned Parenthood," says Qorvis Communications's Stan Collender, a veteran expert on the budget and the congressional politics surrounding it. "It's clearly enabled some members to say, we're going to oppose Planed Parenthood, we're going to oppose the Iran deal any way we can and we're going to shut down the government."

Trump has focused most of his comments and political attacks on President Barack Obama, the media and his primary opponents. But Trump's presence Wednesday at a rally near the Capitol in opposition to the Iran nuclear deal was a reminder to those inside the building of his ability to whip up a potent segment of the Republican political base – the one that would prefer to shut down the government rather than spend federal dollars for Planned Parenthood, any costs associated with the Iran pact or the payments due on the the federal debt.

Congress is facing several major deadlines, chief among them the September 30 due-date for finishing a federal spending package. No one expects Congress to come to agreement on individual spending bills, so lawmakers would need to pass a continuing resolution to keep the government running. Conservatives, upset about surreptitiously filmed videos of Planned Parenthood officials discussing the financial costs of collecting and transporting fetal tissue for research, want to defund the women health clinics and some are willing to use the issue as leverage in passing a continuing resolution. Colleagues expect Texas Sen. Ted Cruz, a candidate for the Republican nomination for president, to again force a federal shutdown by filibustering a spending package.

And while Cruz's antics have irritated his colleagues on both sides of the aisle (Sen. John McCain, Republican of Arizona, called Cruz one of the "wacko birds" of the chamber), it's clear that the shutdown strategy has an appeal among the hard-core, anti-Washington element of the party. That would include Trump, who joined Cruz at the Wednesday Iran rally.

Congress also faces a deadline later this year to raise the national debt limit. And while the Highway Trust Fund was recently declared to be a bit healthier than thought – the Department of Transportation says it has enough cash to last until June of next year – Congress must still pass, by late October, the authorizing legislation allowing department to spend the money.

"It's only logical that [Trump] is having some effect on the Hill," says Stu Rothenberg, an independent political analyst. "He's out there being the dean of anti-establishment rhetoric, fighting for what you believe in. I can't imagine it's not having an effect on the tea party" caucus in the House, Rothenberg adds.

The Trump factor has put Republicans in a quandary: They welcome the energy Trump has brought to the party base, but they don't want him interfering with their business. And they certainly don't want Trump to encourage behavior, such as a government shutdown, that has short-term political benefits for conservatives, but long-term political troubles for the national party.

Asked if Trump was helping congressional Republicans and the party as a whole, Rep. Louie Gohmert, Republican of Texas, said, "I think he is. If [2012 GOP nominee Mitt] Romney had gotten the same number of votes [2008 nominee John] McCain did, Romney would have won," Gohmert said. Trump, Gohmert said, "has gotten people excited again."

But others – while reluctant to outright criticize Trump – bristle at the idea that Trump is affecting their Capitol work. "I don't think that anyone up here is looking to Donald Trump for legislative advice," says Sen. Cory Gardner, Republican of Colorado.

Democrats say they are troubled at Trump's success and alarmed that it could end up affecting the work they do on the Hill. "I think the Trump rally has affected the character of the debate about Iran," says Sen. Tim Kaine, Democrat of Virginia, making it more partisan and apocalyptic. And Florida Rep. Debbie Wasserman-Schultz, who also chairs the Democratic National Committee, castigated Trump pal Cruz for his campaign against Planned parenthood and vowed to make it an issue in the general election campaign.

"Look, you've got Ted Cruz, who – it wasn't enough to actually shut the government down over denying people access to health care, now he's continuing – and he's running for president and a number of them are about to vault us into a fight to shut the government down over whether we fund Planned Parenthood," Wasserman Schultz told reporters at a breakfast Thursday. "Those are the kinds of things that as we move forward and have two nominees, that will be the campaign's focus, the voters' focus."

Rep. Charles Rangel, Democrat of New York, says he thinks Trump has no direct influence on congressional votes, but does exert a more insidious power on Republicans. "Donald Trump is the rare politician people are intimidated by, and for a good reason – and that is, he does not play by the rules," Rangel said. Trump is so unpredictable – and so ready to attack those who take him on – that his Republican colleagues are fearful of engaging with Trump, Rangel adds.