Last week, like most weeks, Sen. John McCain (R-Ariz.) was invited onto a Sunday show, where he complained that U.S.-Israeli relations have “ never been worse ” than they are now. Naturally, this led a different Sunday show to extend another invitation to McCain yesterday, where he repeated the claim.

As a matter of diplomatic history, it remains a debatable point. Let’s not forget that relations between the two allies have hit rough patches several times over the decades, most notably under Ronald Reagan, who repeatedly clashed with Menachem Begin. Haaretz’s Chemi Shalev joked a while back, “[I]f Obama treated Israel like Reagan did, he’d be impeached.”

But even if we put aside McCain’s knee-jerk desire to blame Obama for anything that comes to mind, it’s fair to say American tensions with Israel have reached an awkward, almost uncomfortable, level. Understanding why matters, and the recent, unprecedented partnership between congressional Republicans and Israeli Prime Minister Benjamin Netanyahu, who teamed up to sabotage international nuclear talks with Iran, appears to have undermined the alliance in rather profound ways.

Eugene Robinson’s latest column strikes all the right notes, noting that Netanyahu and House Speaker John Boehner (R-Ohio) “made a colossal mistake … and the move has ricocheted on both of them.”

Why on earth would anyone think it was a good idea to arrange for Netanyahu to speak to a joint session of Congress without telling Obama or anyone in his administration about the invitation? … [I]nviting a foreign leader to speak at the Capitol without even informing the president, let alone consulting him, is a bald-faced usurpation for which there is no recent precedent. […] Netanyahu, for his part, may have thought this was a way to boost his prospects in the upcoming Israeli election, scheduled for March 17. Or he may have fantasized that somehow, by openly siding with the Republican Party, he could snatch U.S. foreign policy out of Obama’s hands. Judging by the pounding he is taking from the Israeli media, he was mistaken on both counts.

Republicans and Netanyahu likely wanted to shift the focus to derailing international diplomacy, but they’ve instead been forced to explain who’s responsible for this fiasco.

The fact that Israeli Ambassador Ron Dermer talked to Jeffrey Goldberg late last week and tried to pin this mess on House GOP leaders – a dubious argument , to be sure – was itself evidence of just how messy this has become.

Last week, even Robert Kagan, a leading neoconservative and no ally of the Obama White House, made a detailed case against the Netanyahu/GOP partnership and urged the Israeli prime minister to cancel his speech to Congress.

Hoping to undo some of the damage, Netanyahu reportedly worked the phones last week, reaching out to Democratic leaders to calm the waters, but Nancy Pelosi and Harry Reid told the Israeli leader what he already knew: by going around the White House to partner with Republicans, Netanyahu has done real damage.

There’s an interesting debate underway about whose screw-up was more severe: Boehner’s or Netanyahu’s. To my mind, it’s a close call – on the one hand, the Speaker took deliberate steps to undermine American foreign policy at a delicate time, siding with a foreign government over his own president, while arguably taking steps to intervene in a foreign election. On the other hand, the Prime Minister needlessly undermined his frayed relationship with the White House, risked damaging Israel’s standing in the U.S., and probably strengthened the diplomatic talks he hoped to ruin.

It was of interest to see former Secretary of State James Baker, a Republican from the Reagan and Bush eras, speak out yesterday about the protocol breach: “[T]he executive branch of government really has the primary power and responsibility and authority to conduct the nation’s foreign policy. It’s not in the Congress, it’s in the executive branch. So our foreign policy benefits when there’s cooperation and so does the issue of U.S.-Israeli relations.”