The White House and some Democrats are livid over congressional Republican attempts to circumvent President Obama's authority to make a nuclear arms deal with Iran. They have a right to be angry — but not to be surprised.

There's a war going on between the executive and legislative branches in which Obama has shown contempt for Congress' constitutional powers, and now, in response, Congress is showing contempt for the president's constitutional powers. It's an unfortunate situation, but it's what Obama has wrought.

The latest development is an open letter to Iranian leaders written by GOP Sen. Tom Cotton, R-Ark., and signed by 46 other Senate Republicans. Released Monday morning, the letter reminds Iran that Obama is negotiating with them on his own, without the formal approval or support of Congress. Obama is not pursuing a treaty, which would have to be agreed to by the Senate, or a joint executive-congressional agreement, which would also require Congress' approval.

"We will consider any agreement regarding your nuclear-weapons program that is not approved by the Congress as nothing more than an executive agreement between President Obama and Ayatollah Khamenei," the Republican senators write. "The next president could revoke such an executive agreement with the stroke of a pen and future Congresses could modify the terms of the agreement at any time."

Just in case there's any confusion, the Republicans remind Iran that the next U.S. president will be inaugurated in January 2017, about 22 months from now, while at least some of the GOP senators who signed the letter will remain in office for many years to come.

The Cotton letter comes on the heels of House Speaker John Boehner's decision to invite Israeli Prime Minister Benjamin Netanyahu to address Congress in what amounted to an extended attack on Obama's Iran negotiations.

It should go without saying that the reason Republicans are doing these things is because they are deeply concerned about a possible Iran deal. But another reason they're acting is because they can. On Iran and before that on immigration, healthcare, and other matters, Obama has pushed his executive authority beyond its proper limits, on the flimsy pretense that he is entitled to act unilaterally if Congress does not pass bills he wants. Could anyone fail to anticipate that in response Congress would stretch its own authority, too?

White House spokesman Josh Earnest quickly condemned the Cotton letter, calling it "a partisan strategy to undermine the president's ability to conduct foreign policy." Democratic Sen. Barbara Boxer, D-Calif., undoubtedly speaking for others in her party, called the letter "bizarre" and "a desperate ploy to scuttle a comprehensive agreement and the chance for a peaceful resolution."

Remember what preceded the Republicans' action. A number of senators, led by Republican Sen. Bob Corker, have been working on legislation to require congressional approval for any Iran deal. "The legislation is a response to the administration's intention not to seek approval or review from Congress for the agreement with Iran, despite a long history of Congress playing a role in international agreements, which has provided added legitimacy and longevity to many of these accords," notes one GOP aide.

The White House response to Corker's initiative was swift. "If this bill is sent to the president, he will veto it," said a National Security Council spokeswoman.

Now, the president's supporters interpret Cotton's letter as the latest in a long line of Republican outrages directed against Obama. "It's safe to say that no president in modern times has had his legitimacy questioned by the opposition party as much as Barack Obama," says the liberal writer Paul Waldman. "But as his term in office enters its final phase, Republicans are embarking on an entirely new enterprise: They have decided that as long as he holds the office of the presidency, it's no longer necessary to respect the office itself."

Actually, things are much simpler than that. Time after time, Obama has told Congress to go to hell. Now Congress is telling Obama to go to hell. It's an entirely predictable development.

Of course, it is still a bad thing. It is not good to invite a foreign leader to address Congress in a campaign against the U.S. president. It is not good to undermine the president's authority to conduct foreign policy. But it's not a good thing to undermine Congress' authority to make laws, either. And to threaten even more undermining in the future, as Obama has done.

It's too bad for Obama that he couldn't persuade Congress to do everything he wanted. That did not give him the right to encroach on Congress's constitutional authority.

Now Congress is pushing back. It's a shame it's come to this, but that's the way things work.