Ted Cruz and Marco Rubio’s Campaign Trail Rivalry Intensifies

— -- While all eyes appear to be focused on Republican frontrunner Donald Trump, there’s a rivalry bubbling up between the two men some think have the best chance to take down the real estate mogul in the GOP presidential field: Sens. Ted Cruz and Marco Rubio.

The two men have been waging a war of words over contradicting policy positions on issues like defense spending, foreign policy, and illegal immigration.

Today, Cruz used an interview on MSNBC's "Morning Joe" to offer some jabs at Rubio, who trails him in a new CBS/NYT poll.

"I honored the promises that I made to the men and women who elected me and Marco did not,” Cruz said, referring to Rubio's support for and co-authorship of the “Gang of 8" comprehensive immigration reform bill in 2013. The bill failed.

“When Marco ran for senate in Florida, he told the men and women of Florida, just like I told the men and women of Texas, if you elect me, I’ll lead the fight against amnesty,” Cruz said. "When we got to Washington, we made different choices. He made the choice to stand with Chuck Schumer and Barack Obama.”

Rubio has previously accused Cruz of flip-flopping on his immigration stance, something Cruz has denied. The two men say they're friends and the attacks aren’t personal, but they seem to be escalating.

Rubio responded to Cruz’s criticism at a campaign stop in West Des Moines, Iowa today, saying that Cruz is a “neo-isolationist” who has weakened America’s national security.

“Ted has consistently voted against defense authorization bills which are the bills that authorize spending on the military. Included in those bills was the Iron Dome Defense of Israel and the paychecks of our men and women in uniform,” Rubio said.

Interestingly, the Florida senator offered a similar criticism of Cruz's relationship with Schumer, a Democrat.

"Ted voted along with Chuck Schumer and other groups to weaken our intelligence gathering capabilities,” said Rubio, referring to Cruz’s support of the USA Freedom Act, which removed the bulk collection of phone metadata by the NSA.

In a speech this morning at The Heritage Foundation, Cruz defended his stance.

"More data from millions of law abiding citizens is not always better data,” Cruz said. “It didn’t stop Fort Hood, it didn’t stop Boston, it didn’t stop Chattanooga...it failed to detect the San Bernardino plot."

Following the speech, Cruz defended himself against a New York Times report that claimed he questioned the judgment and preparedness of Donald Trump and Ben Carson during a private fundraiser. His campaign has called the report misleading and Cruz said he wouldn’t comment on the alleged remarks.

Rubio pounced.

"I never say anything at a fundraiser I wouldn’t say at a public event,” Rubio said. “My message is pretty consistent. Whether it’s in a private meeting with an individual or a group of donors or in a broader setting."

Today’s war of words is one of many that’s broken out between the two men in recent weeks. Cruz has accused Rubio and a super PAC supporting him of spreading false attacks. In late November, the Cruz campaign released an ad where Rep. Jim Bridenstine (R-OK) defended Cruz from attacks by Rubio and his supporters.

On the campaign trail, both men frequently face questions about each other.

At a recent campaign stop in Greenville, South Carolina, a supporter came up to Cruz and asked how he differed from Rubio. Cruz told the supporter there are “marked differences.” While Cruz often plays up their difference on immigration in television interviews, he offered another issue that matters significantly to the evangelical voters he is courting.

“Two of the sharpest differences are on immigration and marriage,” Cruz said. “So on immigration, we’re on opposite sides of that issue. And then on marriage, what Marco has said is that he views the gay marriage decision as the settled law of the land. And I passionately disagree.”