Washington (CNN)Israeli Prime Minister Benjamin Netanyahu described his polarizing trip to Washington as "crucial" as a storm raged over his planned speech to Congress.
6 questions about Netanyahu's visit
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"This is a crucial trip, even a historical one," Netanyahu said as he boarded a flight in Tel Aviv on Sunday. "I will be the messenger of all the people of Israel, including those who agree with me and those who don't agree with me."
"I fear for the fate of the state of Israel, and therefore I'll do everything I can to ensure the security of our future."
A few dozen Democrats plan to skip the speech, the White House isn't done blasting the prime minister, and Republicans -- especially presidential hopefuls -- are using it all as red meat.
In Israel, his visit added an extra layer to a contentious election season.
Why has this become such a massive fiasco? And what does this mean for the future of the U.S.-Israel relationship?
Let's dive in.
1. Isn't support for Israel rock solid in Congress? Why has an Israeli prime minister's visit become so controversial?
The controversy first started because of two words: protocol and snub.
House Speaker John Boehner's announcement that Netanyahu would be addressing Congress took the White House by surprise.
Boehner barely gave the White House any heads up and neither did Netanyahu.
That's despite several high-level interactions between U.S. and Israeli officials in the lead-up to the announcement, interactions that included a phone call between Netanyahu and President Barack Obama and a meeting between Secretary of State John Kerry and the Israeli Ambassador Ron Dermer.
That last meeting took place for several hours, the day before Boehner announced the visit.
It didn't take long for White House officials to call the move a breach of protocol and a snub by Israelis who were enjoying the backing of U.S. officials as Palestinians pressed their case through international institutions.
And then there was the politics of it. Boehner made the invitation soon after Republicans assumed control of both Houses of Congress — and the day after Obama announced in his State of the Union that he would veto the Iran sanctions Republican members are seeking. The invitation had the appearance of scoring partisan political points.
2. OK, so White House officials felt like Netanyahu and Boehner plotted behind Obama's back. But this has got to be about more than a snub, right?
Well, Netanyahu won't be lecturing Congress on any old topic.
Instead, he'll stake out a hardline position on Iran and its pursuit of nuclear weapons, warning lawmakers that ongoing negotiations with Tehran are moving in a dangerous direction -- a lobbying push that Obama implored Netanyahu not to make in the phone call that came just over a week before the visit was announced.
In the process, Netanyahu is expected to stake out a position that undercuts almost every aspect of Obama's approach to dealing with Iran.
That's provoked a strong reaction from many Democrats, who say it's inappropriate for a foreign leader to counter the President's foreign policy in such a high-profile forum.
3. So why is Netanyahu insistent on coming to Congress now?
For starters, it's for the same reason he's facing so much pushback from the White House.
The United States and five other world powers negotiating with Iranian diplomats in Geneva have a late March deadline to reach a framework agreement on curbing Iran's nuclear ambitions.
The Obama administration has invested massive amounts of political capital into negotiations even the president concedes have just about a 50-50 chance of success.
But Netanyahu is convinced the Obama administration would accept a bad deal rather than come away empty-handed, warning recently that the agreement in the works would allow Iran to preserve far too many centrifuges. Netanyahu would like to see Iran give up all its nuclear enrichment capacity, a demand no one considers realistic.
"I am going to the United States not because I seek a confrontation with the President, but because I must fulfill my obligation to speak up on a matter that affects the very survival of my country," Netanyahu said recently in a televised statement, explaining that he needs to lay out his "profound disagreement" with the U.S. and its negotiating partners over the nuclear talks.
Netanyahu added that he needs to address lawmakers before the March deadline "because Congress might have a role with an important nuclear deal with Iran." Specifically, there are two bills in the works that could gum up a deal — one on more sanctions and the other demanding congressional approval of any agreement.
4. It's not the first time Netanyahu and Obama have been at odds over Iran, is it?
Nope. Obama has repeatedly insisted he would rather take no deal than a bad deal with Iran. But Netanyahu, Republicans and some Democratic lawmakers have claimed Obama is going too soft, too soon.
With the help of a dozen Democrats, Republicans unsuccessfully tried to push a bill through Congress last year that would have hit Iran with additional sanctions in the midst of negotiations.
With a new majority in their hands, Republicans renewed that push in January with a watered-down bill that casts the specter of additional sanctions over Iran if it failed to come to the table.
Netanyahu has supported ratcheting up sanctions on Iran, but Obama and his State Department negotiators have insisted it could bolster hardliners in Iran and push Iran away -- rather than closer to -- a peaceful end to Iran's nuclear program.
5. What else is driving Netanyahu?
Israelis will head to the polls just two weeks after Netanyahu addresses Congress and Netanyahu is leaning heavily on a strong national security platform to remain prime minister and keep his party in power.
Netanyahu has been active on Twitter in the last month, posting about the existential threat a nuclear-armed Iran would pose to Israel and playing up his defiant stance in heading to Congress to defend Israel in the face of opposition from even the President of the United States.
Speaking of which, the White House announced that Obama will not meet with Netanyahu during his trip to Washington due to the proximity of the Israeli elections.
While Netanyahu's circle has denied that the elections play a role in his decision to make the controversial visit, there's no doubt the prime minister will be able to play up his address to Congress in the home stretch of the campaign season.
6. Will there be lasting damage to the U.S.-Israel relationship?
The question on everyone's minds in Washington is whether U.S. support for Israel is now becoming a partisan issue.
While several Democrats will be skipping Netanyahu's speech and National Security Adviser Susan Rice recently called Netanyahu's address "destructive" to the U.S.-Israel relationship, widespread support for Israel is unlikely to wane anytime soon.
Opposition to certain policies -- like settlement building in the West Bank -- may be gaining strength, but shifting Democratic views and the recent tensions provoked by Netanyahu's impending visit haven't affected U.S. military assistance and diplomatic support for Israel (and aren't likely to).
Despite the personal tensions, the relationship between the U.S. and Israel has remained close throughout Obama's tenure -- and Israeli officials like to emphasize that ties between the two countries have never been stronger.
However, the deep disagreements on Iran mean that there could be a divergence on a significant policy issue. There have been reports of some breaks in what has traditionally been intensive consultations on the matter.
And though the U.S. has showed no sign of backing away from its defense of Israel in places like the U.N. where the Palestinians enjoy wide support, a nasty, politicized spat between Israeli and American leaders doesn't exactly boost Israel's standing.