The angry forces that propelled President Trump’s rise are beginning to frame and define the rest of the Republican Party.

When GOP House candidate Greg Gianforte assaulted a reporter who had attempted to ask him a question Wednesday night in Montana, many saw not an isolated outburst by an individual, but the obvious, violent result of Trump’s charge that journalists are “the enemy of the people.” Nonetheless, Gianforte won Thursday’s special election to fill a safe Republican seat.

“Respectfully, I’d submit that the president has unearthed some demons,” Rep. Mark Sanford (R-S.C.) said. “I’ve talked to a number of people about it back home. They say, ‘Well, look, if the president can say whatever, why can’t I say whatever?’ He’s given them license.”

Trump — and specifically, his character and his conduct — now thoroughly dominate the national political conversation.

Traditional policy arguments over whether entitlement programs should be overhauled, or taxes cut, are regularly upstaged by a new burst of pyrotechnics.

(Jenny Starrs/The Washington Post)

The dynamic is shaping the contours of this year’s smattering of special congressional elections and contests for governor, as well as the jockeying ahead of the 2018 midterm elections.

[An assault, a victory and then an apology]

“It’s an entirely different atmosphere,” Michael Steele, a former Republican National Committee chairman, said. “The president isn’t ideological, and ideology is no longer the anchor. So when reporters put microphones in candidates’ faces, they’re asking about the president, tweets, character, your moral outlook and not about a particular policy.”

Few Republicans expect party leaders to do anything to lessen the toxicity.

Charlie Sykes, a conservative former talk-show host in Wisconsin and author of the forthcoming “How the Right Lost Its Mind,” said “every time something like Montana happens, Republicans adjust their standards and put an emphasis on team loyalty. They normalize and accept previously unacceptable behavior.”

Those who still navigate by the old maps are having trouble staying the course.

Karen Handel, a conventional Republican running in next month’s special House election in Georgia, has railed against Obamacare, and campaigned alongside House Speaker Paul D. Ryan (R-Wis.), who called her “tested and true.” But she has been scorched endlessly on television for her support of the president her Democratic opponent has claimed “embarrasses our country” and “acts recklessly.”

Other GOP candidates, emboldened by Trump’s success at shattering norms, have ventured further to test the limits of what the electorate can stomach.

Corey Stewart, a former state chairman for Trump’s presidential campaign, has embraced Confederate symbols as his gubernatorial bid has flailed in Virginia, horrifying party leaders ahead of the June 13 primary and forcing the GOP front-runner to respond.

His primary opponent, former RNC chairman Ed Gillespie, has seen his steady, well-funded campaign for governor all but drowned out recently by Stewart’s rage over the effort to remove Confederate statues from public spaces, which Stewart has said is proof that “ISIS has won.” Their primary clashes have been more over style and political correctness than any issue.

Gillespie has kept the edge. “Corey has labeled himself as Trump’s Mini-Me, but the mojo ain’t there,” Shaun Kenney, the former executive director of Virginia’s Republican Party, said earlier this year. But it remains to be seen whether Stewart has damaged the GOP brand for the general election.

Other polished exemplars of the establishment have struggled to set themselves apart.

Handel, a fixture of state politics, has seen suburban voters in her district, which has been in Republican hands since 1979, grow so uneasy about Trump that her once unknown Democratic challenger, Jon Ossoff, has taken the lead in polls.

Appealing to voters weary over Trump’s comportment, Ossoff has seized on Trump’s decision to fire James B. Comey as director of the FBI, which is investigating Russian interference in the 2016 presidential race.

But for some Republican contenders, Trump has been a model — nowhere more so than in deeply red Montana. Gianforte, a wealthy businessman, touted his full-throated support for the president and pledged to “drain the swamp” in his campaign against Rob Quist, a country music artist.

Gianforte’s election-eve eruption capped weeks of frothing frustration within the ranks in Montana and elsewhere about scrutiny of Trump and Republicans in the media, with the Trump-friendly candidate fuming and reacting physically to a question from Guardian reporter Ben Jacobs.

Ryan, who has labored to swing the spotlight away from GOP missteps and toward his agenda, criticized Gianforte’s actions and said, “There is no time a physical altercation should occur.” But he did not rescind his endorsement and, along with other Republicans, plodded forward Thursday reluctant to delve into a character debate. “I’m going to let the people of Montana decide,” he said.

The Republican lurch away from running highly disciplined, by-the-book campaigns on curbing spending and stoking economic growth is, in part, the evidence of how fully Trump has upended the party. Republicans haven’t abandoned the views and positions they have cultivated since Ronald Reagan’s presidency, but instead appear unable to focus on them.

Trump’s barrage of news-making and controversy drives the GOP even at its lowest levels, with his raucous populism and blustering behavior reshaping its identity. Candidates often are either adopting aspects of his persona or finding themselves having to fitfully explain why they back him. Coupled with a national conservative media complex that sears the press as much as it does Democrats, they are navigating a highly charged and volatile environment.

Fox News, the network beloved by Republicans, has also found itself dealing with the right’s disruptive fury and questions of conduct, even among its high-profile hosts. Sean Hannity has been criticized and lost advertisers for promoting a conspiratorial account of the slaying of a Democratic National Committee staffer. Hannity has reacted by charging that “liberal fascists” were conspiring to cripple his career.

Some advocates for the media say that the culture Trump has created within his party is responsible and has had a cascading effect on the way 2017 campaigns have unfolded.

“Before the 2016 campaign, we could at least expect civility from candidates and their staffs,” Lucy A. Dalglish, the dean of Philip Merrill College of Journalism at the University of Maryland, said. “Trump has declared open season on journalists, and politicians and members of his Cabinet have joined the hunt.”

Kathleen Hall Jamieson, a professor at the University of Pennsylvania’s Annenberg School for Communication, added: “By casting the press as the enemy of the American people, Donald Trump has contributed to a climate of discourse consistent with assaulting a reporter for asking an inconvenient question.”

For Democrats, the GOP disarray presents perhaps the ripest opportunity for a blue political wave in over a decade, especially if the Republicans are alienating suburban professionals and independents.

In Georgia, for instance, Democrat Ossoff is running not as a vocal young progressive but a thoughtful, middle-of-the-road and careful Democrat. Republicans Gillespie and Handel are shying away from Trump-style theatrics.

Democrats, who are in the midst of their own political tug-of-war between progressives and centrists, have not yet been able to translate the Republican scandals and Trump tiffs into convincing wins.

Ossoff nearly captured the Georgia seat last month but did not garner enough votes, and the race went to a runoff.

Yet there have been flashes of opportunity: Democrats won two special state legislative elections this week in New York, with one of the pickups coming in a district that Trump won.

In early April, Republicans fended off a strong Democratic challenger in ruby-red Kansas in this year’s first special House election, following last-minute support from Trump and Vice President Pence. Republican Ron Estes won by eight percentage points; two years earlier a Republican had won the seat by 31 percentage points.

Meanwhile, in New Jersey’s gubernatorial campaign, the two leading Republicans running ahead of a June 6 primary — Lt. Gov. Kim Guadagno and Assemblyman Jack Ciattarelli — are dealing with the cloud not only of Trump but of New Jersey Gov. Chris Christie (R), whose tumultuous leadership and bridge-closing scandal has left the state GOP fractured and been a burden on the Republican hopefuls.

Longtime watchers of Trump do not expect him to speak out against Gianforte or to urge his party against the politics of bellicosity.

They recalled that he fiercely defended his then-campaign manager, Corey Lewandowski, when he was accused last year of grabbing a female reporter’s arm. Trump himself once said of a protester at one of his campaign rallies: “I’d like to punch him in the face.”

In Sicily at a G-7 summit on Friday, Trump praised Gianforte for a “great win in Montana.”

In the Trump era, it is far from clear what is over the line — or even if a line exists any more.

“There is a total weirdness out there,” Sanford said. “People feel like, if the president of the United States can say anything to anybody at any time, then I guess I can too. And that is a very dangerous phenomenon.”

Mike DeBonis and Paul Schwartzman contributed to this report.