GOP rivals hammer Rubio

The Republican field is ganging up on Marco RubioMarco Antonio RubioRubio: McCabe 'should've been allowed to finish through the weekend' For Tillerson, bucking Trump became a job-killer At least six dead after pedestrian bridge collapses on cars in Florida MORE.

The Florida senator has been assailed in recent weeks by a host of GOP rivals, including former Florida Gov. Jeb Bush, Sen. Ted CruzRafael (Ted) Edward CruzCruz says Cambridge Analytica assured him its practices were legal Dem battling Cruz in Texas: ‘I can understand how people think this is crazy’ Overnight Tech: Facebook faces crisis over Cambridge Analytica data | Lawmakers demand answers | What to watch for next | Day one of AT&T's merger trial | Self-driving Uber car kills pedestrian MORE (Texas), Sen. Rand PaulRandal (Rand) Howard PaulTrump formally sends Pompeo nomination to Senate Spending bill delay raises risk of partial government shutdown support Overnight Defense: Senate sides with Trump on military role in Yemen | Dem vets push for new war authorization on Iraq anniversary | General says time isn't 'right' for space corps MORE (Ky.) and New Jersey Gov. Chris Christie. The number of crosshairs trained upon Rubio’s back is unusual, even by the rough-and-tumble standards of this year’s presidential cycle.

But the attacks also point to Rubio’s potential. Many observers believe that his poll ratings, which show him in third place nationally and in the first caucus state of Iowa, underplay his strength.

The Florida senator is the leading candidate with some appeal to the GOP establishment — something manifestly not true of the insurgent front-runner Donald TrumpDonald John TrumpKoch-backed group launches six-figure ad buy against Heitkamp Anti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight MORE or the second-place Cruz. That means other candidates who are dependent upon centrist support need to cut Rubio down if they are to stand any chance of emerging as the party’s 2016 standard-bearer.

“Rubio is by almost everyone’s account doing third-best, and rising,” said Susan MacManus, a professor of government at the University of South Florida. “But he is very different from those other two, who are very anti-establishment. So for all the others who also want to appear different from Trump and Cruz, they have to elevate themselves and take down Rubio.”

Many of his rivals, and their allies, have been busily trying to do just that.

On Tuesday, Right to Rise, the main super-PAC supporting Bush, released an ad suggesting Rubio had missed “important national security briefings” to attend fundraisers. “Politics first — that’s the Rubio way,” the ad’s narrator intoned.

The ad drew immediate pushback from the Rubio camp, with the senator’s communications director, Alex Conant, tweeting that its contention that the candidate had missed a briefing on the recent terrorist attacks in Paris was “wrong. @marcorubio attended Intel briefing on Paris attack.”

Rubio’s missed Senate votes while on the campaign trail have been highlighted by other rivals, however. Christie picked up on Rubio’s failure to vote on the year-end $1.8 trillion spending package, despite having stated he was opposed to it.

“Only in Washington could you have the guts to say I’m against something that you have a vote to vote no on, and then just not go. And then put out a press release after it gets passed to say, ‘This is why I was opposed to it,’” Christie said at a town-hall event in Iowa on Tuesday.

“Well, dude, show up to work and vote no, right?” Christie continued. “Just show up to work and vote no, and if you don’t want to, then quit.”

Rand Paul, who has made a habit of issuing acerbic tweets on Dec. 23 to mark the faux-holiday of Festivus and its tradition of grievance-airing, this year wrote, “To my absentee friend @marcorubio, I didn't put your $170k+ salary in my waste report today. But I could have #Festivus.”

Paul’s chances of becoming the GOP nominee appear minuscule at this point, but both Bush and Christie are busily competing with Rubio in the establishment lane of next year’s contest. In New Hampshire, for instance, Christie is snapping at Rubio’s heels, with 11.5 percent support to Rubio’s 12.8 percent, according to the RealClearPolitics average. The combative New Jerseyan will hope that persistent attacks can peel off Rubio’s supporters.

A different dynamic is in play in the case of Cruz. He and Rubio have engaged in a long-running dispute — mainly over immigration policy — that was especially fiery during the most recent GOP debate, held earlier this month in Las Vegas.

Although Cruz clearly appeals to a more conservative cohort than Rubio, he appears to see him as a serious threat. The Texan has referred at times to the “Rubio-Schumer amnesty plan” on immigration. A few days before the Las Vegas debate, Cruz asserted in an interview with MSNBC’s “Morning Joe” that Rubio “has far too often agreed with Hillary ClintonHillary Diane Rodham ClintonKoch-backed group launches six-figure ad buy against Heitkamp Trump keeps up 'low IQ' attack on Maxine Waters GOP leaders to Trump: Leave Mueller alone MORE and Barack ObamaBarack Hussein ObamaWater has experienced a decade of bipartisan success Kentucky candidate takes heat for tweeting he'd like to use congressman for target practice What’s genius for Obama is scandal when it comes to Trump MORE.”

Cruz could be playing a complicated game, some insiders say. While he would certainly like to see a Rubio decline for its own sake, such a change would also have the likely effect of keeping the greatest number of pro-establishment candidates in the race — something which would help Cruz by splitting the center-right vote.

Rubio has not been shy about hitting back, drawing attention to past statements by Cruz that sound more equivocal on immigration reform than his current rhetoric.

But there can be dangers for candidates in attacking each other too fiercely in a multi-candidate field, as past election cycles in both parties prove. Back in 2004, for instance, Democrats Howard Dean and Richard Gephardt did trenchant verbal battle in the run-up to the Iowa caucuses — which then-Sen. John KerryJohn Forbes KerryKentucky candidate takes heat for tweeting he'd like to use congressman for target practice Breitbart editor: Biden's son inked deal with Chinese government days after vice president’s trip State lawmakers pushing for carbon taxes aimed at the poor MORE (D-Mass.) won, his first step on the path to claiming the nomination.

“I think voters have come to expect negativism,” said MacManus. “But they haven’t come to like it.”