Donald Trump's closing speech at the Republican National Convention offered a "dark and frightening" vision of a United States with him as president, according to a former GOP speechwriter.

Mary Kate Cary, who wrote speeches for former president George H.W. Bush, says she was disappointed by Trump's address on Thursday night, because he offered up "platitudes" without sharing any specifics about his policies or plans for his administration. His speech was also too long, and lacking in humour and anecdotes to make him seem relatable, she said.

"If he had a different tone that would have helped," Cary told CTV News Channel on Friday. "He was yelling almost the entire speech. There was no warmth or compassion there, despite what his children had said about him all week."

Political science professor Jeffrey Berry, of Tufts University, said Trump came across as disciplined, coherent, masculine and forceful. "He did come across as arrogant, but also came across as confident," Berry told CTV News Channel. "Maybe that reassures some Americans that we're headed probably in the right direction. (It) probably offends others though."

'I am the Law and Order candidate'

Trump made a number of broad proclamations in his speech, including a sweeping promise to end crime and violence in the United States. "The crime and violence that today afflicts our nation will soon come to an end," he said. "Beginning on January 20th, 2017, safety will be restored." Trump also declared that "Nobody knows the system better than me, which is why I alone can fix it."

Cary says proclamations like that leave her asking the question: "How?"

"Some people might find that reassuring," she said," but people outside the (convention) hall like me say, 'How are you going to stop the violence?'"

Berry said law and order has been a common theme in the Republican Party, dating back to 1968, when then-nominee Richard Nixon touted it as a solution to the race riots sweeping through American cities. "It has a very strong racial connotation," Berry said. "Law and order is about black disorder, and what Trump was saying is that in a Trump administration, things are going to be different."

Trump spoke at length about the recent attacks on police officers in the United States, but did not explicitly refer to black Americans at any point in his speech. Instead, he spoke broadly about "An attack on law enforcement is an attack on all Americans," he said, adding that he will appoint the "best and brightest" prosecutors and law enforcement officials.

"I have a message to every last person threatening the peace on our streets and the safety of our police: when I take the oath of office next year, I will restore law and order to our country."

Courting voters

Berry said Trump's speech also seemed to give up on courting Hispanic voters, with its aggressive depiction of immigration. "Nearly 180,000 illegal immigrants with criminal records, ordered deported from our country, are tonight roaming free to threaten peaceful citizens," Trump said in his speech.

Berry added that Trump's rhetoric will likely fail in attracting moderate voters. "I think the Republican convention was a lost opportunity," he said. "He seemed to be appealing to those who are already going to vote for him: Conservative white Republicans. The few voters that are in the middle, the swing voters, are more moderate and I don't think they can be scared into voting for Republicans."

Cary said she would have liked to hear how Trump plans to work with the Republican-packed Congress, what types of people he'll want in his administration, or what he intends to accomplish in his early days as president. "There was none of that," she said. "It was a very emotional appeal that really was designed to whip people up."

Trump told the convention that his "first task" will be to "liberate our citizens from the crime and terrorism and lawlessness that threatens our communities."

On Thursday, Cary tweeted that Trump's speech offered a "dark vision of the future," with no "uplifting vision or call to action" that Republicans can rally behind.

"It was a very disturbing speech to me with a very dark vision for this country," she told CTV News Channel.

"He made the case for a Trump presidency built on the idea that America is at the abyss," Berry said.