When it was revealed that Israeli Prime Minister Benjamin Netanyahu had accepted Republicans' invitation to speak to a joint session of Congress this March, it provoked a political firestorm. Netanyahu's speech would almost certainly focus on Iran's nuclear program, an issue on which he and President Obama are fundamentally at odds. Many observers saw the speech as a grave breach of protocol by Netanyahu and, by Congressional Republicans, a naked attempt to undermine Obama's foreign policy.

Netanyahu's apparent goal was to bolster Republican opposition to Obama's Iran talks and to encourage along new US sanctions on Iran that would blow up the talks. But, now, it appears that Netanyahu's gambit is blowing up in his face. Congressional Democrats are furious with Netanyahu, and the speech may well have caused them to put off a critical vote on Iran sanctions, thus putting Netanyahu's goal further out of reach.

While some think the speech is also an attempt to boost Netanyahu's poll numbers at home in advance of March 17 elections, that's probably not his core motivation, and in case it's not clear that it will help his political standing. The speech probably hasn't buoyed Netanyahu yet in Israeli polls and opposition parties are seizing on it as a sign of Netanyahu hurting the alliance with America. Ultimately, the speech seems to be a sincere bid to head off a nuclear deal Netanyahu sees as catastrophic — but that bid is backfiring.

Democrats are really, really pissed at Netanyahu

As of Thursday, Vice President Joe Biden, who would normally attend a joint session, had still not confirmed whether he would attend the speech, citing scheduling constraints. Meanwhile, dozens of Congressional Democrats are threatening an outright boycott. Senate Minority Leader Harry Reid has said attending is a "personal choice" for members; second-ranking Senate Democrat, Dick Durbin, is thinking about joining the boycott.

Things like this aren't supposed to happen in the US-Israel relationship. For decades, support for Israel has been overwhelmingly bipartisan. Pro-Israel bills regularly pass by unanimous or near-unanimous margins.

So for this many Democrats to threaten to snub the prime minister, it's a big deal. Netanyahu accepted a Republican invitation to deliver a high-profile speech slamming Obama's foreign policy. In their minds, that's an unacceptable insult to both the president and the pro-Israel Democratic Party. This angry reaction could end up undermining the very thing that Netanyahu wants to accomplish.

One of Netanyahu's core goals with this visit is to build congressional support for a bill imposing new sanctions on Iran. He thinks the US-led negotiations with Iran over its nuclear program are a sham that will do more harm than good. Democrats are torn between the "pro-Israel" position of supporting Netanyahu with Iran sanctions versus the pro-Obama position of opposing sanctions.

Several days after the speech was announced, a group of 10 key Senate Democrats agreed not to vote for any new Iran sanctions before March 24 — the deadline for a framework agreement with Iran on the nuclear program. This was a gift to the White House, promising no deal-killing sanctions for at least a few weeks. Sen. Robert Menendez, the Democratic co-author of the sanctions bill, said the speech had "absolutely no effect" on his decision to delay the sanctions vote. But that's pretty hard to believe.

Sen. Joe Manchin, one of those 10 Democrats, told the New York Times that "for the prime minister to accept [the invitation to speak to Congress] made it extremely political, knowing how the invitation played out."

"On substance this has backfired on Netanyahu ... quite dramatically," Natan Sachs, a fellow at the Brookings Institution's Center for Middle East policy, told me.

"From what I hear," Sachs said, "if this were the first incident between Obama and Netanyahu, it would be one thing. But this is not nearly the first."

It's certainly not; for some years, Netanyahu has been criticizing Obama, often quite openly, and working closely with Republicans and GOP donors. The furious reaction to Netanyahu's speech, in other words, isn't solely about this one address. It's the all-but-inevitable reaction to Netanyahu's repeated attempts to play partisan politics.

Bibi hasn't been hurt at home yet, but opposition parties see an opening

There's a second possible rationale for Netanyahu's address: domestic politics. Netanyahu's Likud Party is in a neck-and-neck race against the center-left coalition Zionist Camp. The Israeli elections are scheduled for March 17; Netanyahu's address to Congress is slated for March 3. The two are so close that the White House has announced it will not meet with Netanyahu, so as to avoid the appearance of unduly meddling in Israel's elections.

Since the controversy over the speech broke in late January, Netanyahu's poll numbers have actually gone up. Obama isn't very popular in Israel, and Israelis tend to be closer to Netanyahu than Obama on the Iran issue.

Still, according to Brookings fellow Sachs, Netanyahu's recent gains aren't really about the Congress dispute, but mostly about some in-fighting among right-wing parties, and there's still a potential for the speech to burn Netanyahu in March.

"Israelis, by and large, don't like it when their prime minister quarrels with the United States"

Down the line, Netanyahu's speech could end up hurting him. A recent poll found that a plurality of Israelis wanted Netanyahu to cancel his speech to Congress. Netanyahu's opponents, sensing vulnerability, have been attacking him on the speech.

Michael Oren, Netanyahu's former Ambassador to the US who's now running for Knesset with the center-right Kulanu party, called on Netanyahu to cancel. The speech "created the impression of a cynical political move," Oren said, "and it could hurt our attempts to act against Iran."

Normally, Israelis don't pay a lot of attention to fighting between Democrats and Republicans. But "Israelis, by and large, don't like it when their prime minister quarrels with the United States," Sachs says. A mass boycott by Democrats, or a high-profile skip by someone like Biden (who should be visible on camera), could alarm Israeli voters concerned about the US-Israel relationship.

If congressional Democrats back down from their threatened boycott, which Sachs thinks is more likely, Netanyahu might still come out ahead. "For most voters, especially in the core base on the right and I think center right, here's Bibi doing something that opposition leaders cannot do: speak the way he does with his English and this reception from Americans," he says.

So we don't actually know how this speech will play in Israel. And nor, probably, does Netanyahu. Which means it's probably exactly what it seems like: a desperate, and backfiring, attempt to stop the US from making what Netanyahu sees as a catastrophic deal with Iran.

"If you assume two things, then this was a rational decision," Sachs says. "You have to believe [any likely deal with Iran] is absolutely terrible for Israel, and Netanyahu does. [And] you have to think a deal is possibly imminent."

"If you think that, then angering a lot of Democrats, angering a president, breaking some protocol — all those pale in comparison," he concludes. "If you're to try to stop a historically terrible thing for the national security of your country, and you think it's imminent, then it's rational to try and do this."