Jeb Bush touts willingness to monitor cell phones in new TV ad slamming frontrunners
Former Florida Governor Jeb Bush speaks on stage with conservative political commentator Sean Hannity at the annual Conservative Political Action Conference (CPAC) at National Harbor, Maryland, outside Washington, on February 27, 2015 (AFP Photo/Nicholas Kamm)

Backers of Republican presidential candidate Jeb Bush are going on the attack against rivals Donald Trump, Ted Cruz and Marco Rubio in a new TV ad that will be broadcast in early voting states.

The ad comes less than a week after a Muslim couple, who the FBI says were radicalized, killed 14 people in a shooting spree in San Bernardino, California, that heightened fears among Americans about Islamic State militants.

Hours after New York billionaire Trump proposed a ban on Muslims entering the United States, Bush's SuperPAC, Right to Rise, released an ad that ridiculed Trump as "impulsive and reckless."

The aim of the advertisement is to portray former Florida Governor Bush as ready to take on the job as commander-in-chief and dismiss some of his chief rivals as ill-prepared for the White House.

The ad is to be broadcast in the early voting states of Iowa, New Hampshire, South Carolina and Nevada as well as nationally on the Fox News Channel.

Texas Senator Cruz is criticized in the ad for voting in the Senate against a bill that limits the government’s ability to collect and monitor Americans' cell phone data.

And the ad attacks Florida Senator Rubio for a history of missed votes and attendance at committee hearings in the Senate.

The president's Oval Office desk is shown in the ad with the words: "When the attacks come here, the person behind this desk will have to protect your family. Will he be impulsive and reckless, like Donald Trump? Will he have voted to dramatically weaken counter-terrorism surveillance, like Ted Cruz?

"Will he have skipped crucial national security hearings and votes just to campaign, like Marco Rubio?

The Right to Rise organization, which began the campaign last summer with more than $100 million to spend, until now has produced television ads playing up Bush's record as the chief executive in Florida.

The ad reflected a new, combative phase of the campaign as the start of the voting approaches in the race for the 2016 Republican presidential nomination. Iowa kicks off the race to the November 2016 election on Feb. 1.

Bush, in a tweet on Monday, called Trump's proposal to refuse entry to any Muslims to the United States "unhinged." He is trying to fight his way back into a Republican race that has been dominated by Trump for months.

(Reporting By Steve Holland; Editing by Robert Birsel)