One year ago, Donald Trump rode down the lobby escalator at his midtown Manhattan office tower and launched the presidential campaign that upended Republican politics — a campaign that now may be facing a make-or-break crossroads.

"Hopefully, we're gonna make it a worthwhile year," Trump told supporters Thursday in Dallas in celebrating his first 12 months as a presidential candidate.

Yet, despite his history-making run to the presidential nomination, Trump continues to face criticism from Republican lawmakers and is now looking at a loss of support in the polls after his comments following the terrorist attack in Orlando.

Read more: American comic Michael Ian Black launches book to teach children about 'beasty' Donald Trump

"I think we're seeing some of the weaknesses of Donald Trump as a general election candidate," said Cal Jillson, a political science professor at Southern Methodist University in Dallas.

Trump, whose celebrity-fueled candidacy was initially dismissed as a joke, pulled off a history-making run in the Republican primaries, but party members noted that the electorate in November will be bigger and more diverse.

Matt Mackowiak, an Austin-based Republican consultant who hasn't decided whether to vote for Trump, said he is concerned that the presumptive GOP nominee is "mistaking success in the primary for success in the general election."

The Herald:

Trump backers who gathered in a honky-tonk ballroom near downtown Dallas predicted their man would prevail because so many Americans are tired of politics as usual, a key part of Trump's appeal.

Tyson Guin, 45, a risk manager from Frisco, Texas, said he expected Trump's success over the past year. "He knows how to sway people," said Guin.

However, truck driver Chelly Nail, 46, of Burleson, Texas, said she was surprised by how far he's come, but added: "I'm glad to be a part of American history."

Saying the country needs changes, Nail said she likes Trump's "beliefs, his attitude, his determination."

Read more: Republican Presidential nominee Donald Trump to face protesters in Scotland at Turnberry

While new polls show Trump falling further behind presumptive Democratic nominee Hillary Clinton, analysts noted that nearly five months remain in the campaign — and Trump's campaign has been different from the start.

In his announcement a year ago, Trump's harsh comments about Mexican immigrants — "they’re bringing drugs; they’re bringing crime; they’re rapists" — were the first of a string of controversial statements that would have sunk most candidates.

During his campaign, Trump questioned the wartime heroism of 2008 GOP nominee and former Vietnam POW John McCain, suggested Fox News anchor Megyn Kelly asked him tough debate questions because she was menstruating and said he wouldn't mind seeing supporters punch protesters in the face.

The Herald:

The Clinton campaign highlighted many of Trump's more acerbic comments in a video marking his campaign anniversary. "Has it only been a year since Donald began his campaign?" the video asks. "It feels longer ... Much longer ... Too long."

Yet millions of Republican voters said they liked his verbal assaults on "political correctness" and his attacks on Republican "establishment" politicians.

The first-time candidate — though one with exceptionally high name recognition — also tapped into people's anxieties over illegal immigration and free trade deals that, some believe, send American jobs overseas.

Trump "represents the degree of frustration, anger, and disappointment there is within the Republican Party," said Stuart Rothenberg, founding editor and publisher of The Rothenberg & Gonzales Political Report.

Now comes a different kind of electorate.

The Republican primaries drew more than 30 million voters. That's a record number, to be sure, but the 2012 race between President Obama and Mitt Romney drew nearly 130 million to the polls, including independents who are suspicious of Trump.

Read more: Donald Trump's Turnberry golf course reopens after £200m renovation

Though he wrapped up the nomination after winning the Indiana primary on May 3, Trump has had trouble consolidating the support of other Republican politicians. Most of them criticized his claims that a federal judge in a fraud lawsuit against Trump University could not be fair because of his "Mexican heritage."

Since Sunday's terrorist attack in Orlando, a mass shooting that killed 49 people, Trump has expanded his call for a temporary ban on Muslims coming into the United States and suggested that President Obama has more sympathy for terrorists than everyday Americans.

For their part, Obama and Clinton have denounced Trump for "dangerous" and irresponsible comments that Islamic State militants will try to use to attract new recruits for attacks on the U.S. — and few Republican lawmakers have come to his defense.

Trump's equally aggressive response to last year's terrorist attacks in Paris and San Bernardino, Calif. — including his initial call to temporarily ban Muslims from entering the United States — seemed to benefit him among Republican voters. So far, his response to the attack in Orlando may be having the opposite effect within the electorate as a whole.

Factoring in a rush of new polls, the current RealClearPolitics average of polls gives Clinton a roughly 6-point lead in a head-to-head matchup with Trump. While the Manhattan real estate mogul continues to do well with rank-and-file Republican voters, he is losing ground with independents and has record-high disapproval ratings from women and minority voters.

Trump and his backers quickly point out that Clinton also has low approval ratings herself, and the New York businessman is the only thing standing in the way of a return to the White House by her and former president Bill Clinton.

Radio host Hugh Hewitt, who recently called on the Republicans to dump Trump at next month's GOP convention in Cleveland, reversed himself in a Washington Post op-ed by saying, "Trump alone can draw a real contrast with Clinton about what government will look like going forward."

Whether Trump can put together a winning general election coalition in the months ahead, however, is open to question. Rothenberg, for one, described himself as "skeptical," but added that "he's done remarkable things so far."