Washington: US Republican presidential front-runner Donald Trump faces a tough test on Tuesday when the party's key primaries will be held in four states of Hawaii, Idaho, Michigan and Mississippi as the gap between him and his rivals has narrowed.
The four State primary is considered to be decisive for the Republican front-runner as an impressive show would put him on the path of commanding lead.
A series of polls released on Monday indicated that 69-year-old real estate tycoon is loosing the momentum in some of the key States like Michigan and Florida.
Though still in the lead, the popularity gap between him and his other rivals have narrowed down considerably.
For instance, the gap between him and Marco Rubio has come down from a 20 point to juts eight points now.
Meanwhile, Rubio strongly refuted reports that he is dropping out of the race.
In Florida, Trump launched a advertisement campaign against Rubio.
"Lightweight Senator Marco Rubio is a dishonest person.
He has cheated with credit cards, and does favours for lobbyists. In my opinion, he is a total crook and I am doing the people of Florida a great favour by further exposing him," Trump said in a statement.
"In addition to everything else, he is an absentee Senator with one of the worst voting records in the history of the United States Senate, instead preferring to spend his time begging for campaign contributions," he said.
In a related development, Paul Ryan, Speaker of the US House of Representatives, called both Trump and Senator Ted Cruz to discuss with them the party s agenda.
This was part of his effort to efforts to craft a bold, election-year agenda, his aid said.
The Politico reported that the Trump campaign has introduced new security measures in view of the increasing frequency of protesters at his rallies.
This includes having security personnel in plain cloths.
At one of the campaign event, some protesters were stripped away first and removed individually by security personnel, while others who remained huddled together were slowly pushed en masse out of the airport hangar where the rally was held, Politico reported.