Trump foes shake up US Republican convention

A Texas delegate yells after the temporary chairman of the Republican National Convention announced that the convention would not hold a roll-call vote on the Rules Committee's report and rules changes and rejected the efforts of anti-Trump forces to hold such a vote at the Republican National Convention in Cleveland, Ohio, US July 18, 2016. [Photo/Agencies]

The gathering opened on Monday afternoon in the shadow of racially tinged killings of police officers and black men, and as protesters for and against Trump faced off in a plaza a few blocks from the convention, shouting slogans at each other, separated by a wall of police.

Trump allies planned to promote what he has billed as a tough line on law and order and national security in speeches on Monday night.

Sunday's shooting of three policemen in Baton Rouge, Louisiana - a targeted attack that may have been in retaliation for a series of police killings of black Americans - hung over the gathering.

Trump lashed out at Obama, who he said "doesn't have a clue," after the police officers' deaths in Baton Rouge, nearly two weeks after police fatally shot a black man there and after another such death near St. Paul, Minnesota, both of which sparked nationwide protests.

Five policemen were also killed in an ambush in Dallas this month.

Trump has sought to position himself as the law-and-order candidate in an echo of Richard Nixon's successful presidential campaign of 1968.

Iowa's Republican Party chairman, Jeff Kaufmann, said the top issue a month ago for voters in the state was the economy. Now, he said, he was hearing concerns about security.

"Rightly or wrongly, the shootings that we've had have vaulted, not just national security in terms of external terrorism but also the knowledge that terrorism is occurring within our country," Kaufmann said.

Such concerns might lead voters to choose Trump over Democratic candidate Hillary Clinton in November, he said.