WASHINGTON — Just as the Pentagon is set to unveil its budget proposal, House Armed Services Chairman Mac Thornberry is urging congressional budget writers to add as much as $23 billion to the expected request for a $525 billion base budget and a $59 billion war budget.

But the Texas Republican's call, made in a letter to House Budget Committee Chairman Tom Price, R-Ga., is most striking because it was co-signed by 33 HASC Republicans, four of them from the fiscally conservative Freedom Caucus — a signal that the battle lines on defense spending may be blurring.

While four members — Rep. Jim Bridenstine, R-Okla.; Rep. Mo Brooks, R-Ala.; Rep. John Fleming, R-La.; and Rep. Trent Franks, R-Ariz. — is hardly a stampede, it appears emblematic of a change over last year, when pro-defense Republicans battled about the budget not only with Democrats, but staunch deficit hawks in their own party's right flank. A committee aide said the number of co-signers was a high for a chairman's "views and estimates" letter.

In the wake of the Islamic State-inspired attacks in Paris and San Bernardino, California, and with an election looming, more Republicans are drifting toward positions favoring defense spending, according to Todd Harrison, director of defense budget analysis at the Center for Strategic and International Studies.

"I think that many more Republicans now are siding with the defense hawks, rather than the fiscal hawks, especially in an election year," Harrison said. "The security environment deteriorating is part of it, but the politics have changed, deficits have gone down, people are less concerned with the overall deficit and more concerned with security. We see that sentiment reflected in Congress."

To be sure, a significant number of Freedom Caucus members retain fiscally conservative positions, pushing the House Budget Committee for a proposal that complies with Budget Control Act (BCA) caps, which were relaxed in 2016 and 2017 by the budget deal. To put the cap back in place for 2017 would amount to a $30 billion cut for the Obama administration's expected budget proposal.

Yet deficit reduction may not have the same public backing it once did. According to a Pew Research poll published last month, just 56 percent of respondents said reducing the deficit should be a priority for the president and Congress, down from 64 percent who said so last year and 72 percent in 2013, when the issue hit peak popularity.

Strengthening the nation's economy and defending the country from future terrorist attacks, neck and neck at 75 percent each, stand at the top of the public's priority list for the president and Congress in 2016. The budget deficit is toward the middle of its list, alongside issues such as reducing crime and dealing with the problems of poor and needy people, according to Pew.

Thornberry's Feb. 5 letter to the House Budget Committee chairman, which was made public Monday, argued that "an adequate national defense requires significantly more funding" and that the Bipartisan Budget Act of 2015 set $59 billion for the 2017 Overseas Contingency Operations (OCO) budget as a minimum — though some key Democrats see it as a maximum.

The budget deal treated OCO, which is exempt from BCA caps, as the overflow receptacle for billions of dollars in base budget requirements. Now HASC Republicans are concerned that if the OCO stays at $59 billion, OCO requirements based on expanding national security needs "will cannibalize funding for base requirements."

"Should the President's budget request break faith with the BBA, we recommend House Republicans insist upon at least an additional $15 - $23 billion," Thornberry wrote, "depending on how much of the designated funding in OCO for base requirements is consumed to address valid emergent threats, to cover the national defense base requirements in the upcoming budget resolution and to enforce the executive branch's agreement in the BBA."

Even if they agree with Thornberry, it is unclear how pro-military deficit hawks will reconcile their beliefs when it comes time to vote for a budget. Brooks — a co-signer who is on the HASC and in the Freedom Caucus — told a reporter he supported adding to defense as Thornberry proposes, but he reportedly said that "there's not a snowball's chance in hell" he would vote for a budget that complies with the BBA.

"National security is the number one priority of the federal government, and if more money is needed to protect American lives from the various threats around the planet, then we need to come up with the money," Brooks said last week. "I support coming up with the money, but we have to do it in a financially responsible way, and that means we have to take the money from lesser priority items and not simply steal more money from our children and grandchildren in the form of a greater debt obligation."

Thornberry, in his argument for defense spending, contextualized an oft-repeated quote from the then-Joint Chiefs chairman, Adm. Mike Mullen, who said: "The most significant threat to our national security is our debt."

That, Mullen went on to say, is because "the strength and the support and the resources that our military uses are directly related to the health of our economy over time."

"Our committee Members agree that the debt is a threat to our security," Thornberry wrote. "Clearly, Admiral Mullen was not suggesting that we should fix the national debt on the backs of the men and women who volunteer to serve our nation in the military."

Although President Obama's national security strategy is a favorite target of Republicans, Thornberry wrote the expected 2017 Pentagon budget is 19 percent lower than the level Obama protected in his 2010 budget request. Reduced budgets of recent years are attributed to the Budget Control Act and "self-imposed efficiencies."

"Any sober assessment of the last seven years would conclude that cutting resources for national defense has neither controlled the debt nor made us safer," Thornberry wrote.

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