The crisis in Ukraine got even worse on Thursday with the collapse of the ruling coalition in Ukraine's parliament. Two of the biggest parties in the ruling coalition withdrew their support, leaving Prime Minister Arseniy Yatsenyuk without enough votes to continue governing, so he resigned.

This is another setback for the country in a crisis that, by the time new elections are held in October, will have stretched on for almost a year. In the meantime, the Ukrainian government could be weakened at a time when Russian-backed separatists are wreaking havoc in the country's east. At the same time, Ukraine is struggling with some of the still-unaddressed internal issues that helped spark the mass protests that toppled the government last fall.

Why did the ruling coalition collapse? And why are Ukrainian politics so unusually bitter and divided? Read on to find out. A big takeaway is that the current crisis is a reminder that Ukraine's problems have always been partly internal, and many of those issues haven't been resolved.

Why did the governing coalition collapse on Thursday?

The turmoil of the last year — the ouster of the pro-Russian President Viktor Yanukovych, Russia's annexation of Crimea, and a continued fight against pro-Russian rebels in eastern Ukraine — has reshaped the political landscape. But the current parliament was elected before those events.

In the other words, much of the current parliament was part of the government that Ukrainians protested last fall. As the Washington Post puts it, "many critics argue that the existing parliament, elected in 2012, is riddled with corrupt and intransigent lawmakers held over from the previous government that the protesters fought to get rid of." Crucially, though, the government that fell this week was led by parties that were part of the opposition under Yanukovych.

Much of the current parliament was part of the government that Ukrainians protested this fall

In a Thursday speech announcing his resignation, Prime Minister Yatsenyuk argued that obstructionist members of parliament were making it impossible to do his job.

How dysfunctional has Ukraine's parliament become?

Ukraine's legislative body, the Verkhovna Rada, is almost ungovernable, and has been for some time.

"The fact is that today you failed to vote for the laws, and I have nothing (with which) to pay wages of policemen, doctors, teachers; nothing to buy a rifle with, nothing to fuel an armored personnel carrier with," Yatsenyuk said to the parliament in his resignation speech. "Today you failed to take a decision to fill the gas storages to allow us to live through the winter, to at last free ourselves from dependence on Russian gas."

Indeed, the body's politics have become so bitter that in recent years, fistfights have been a recurring phenomenon. The most recent incident occurred this week, during a debate over whether to send more troops to fight Russian separatists. An argument on the floor of the legislature came to blows:

Why is the Ukrainian politics so bitter?

Ukrainian politics is deeply divided between, roughly speaking, east and west. While this divide is more complicated than just demographics, and politically has to do with much more than foreign policy, over the past year it has played out that way. The eastern and southern ends of the country have a lot of Russian speakers and close cultural and economic ties to Russia. Many people in the east and south — including some who are descended from Russians who moved to Ukraine during the Soviet and Russian Imperial eras — look back fondly on the Soviet era as a time when Ukraine was part of a great empire.

Most people in the western and northern parts of the country feel differently. They feel greater kinship to the west, and many see the Soviet era as a period when Ukrainians faced persecution at the hands of their Russian masters. Again, in effect this divide is much more complex than Russia versus Europe, but that is a rough proxy for thinking about how it splits.

Here's a map that shows the ethnic and linguistic composition of Ukraine:

Now compare this to a map of the 2010 presidential election:

As you can see, the Russian-speaking regions of Ukraine line up almost perfectly with the regions that voted for President Yanukovych (pronounced Janukovych) in 2010, while the Ukrainian-speaking areas voted overwhelmingly for his more Western-leaning opponent, Yulia Tymoshenko. The prime minister who just resigned, by the way, was a political ally of Tymoshenko.

It's hard for legislature to get anything done when its members are so starkly divided.

Those lines have only hardened in the last year. The ouster of Yanukovych convinced many Russian-speaking Ukrainians that the system was rigged against them, while Russia's annexation of Crimea and its support for pro-Russian rebels has made people in the west of Ukraine more fearful of Russian aggression. And this sense of division — which at times extends to legislators literally speaking different native languages — makes cooperation on other issues harder. It's hard for legislature to get anything done when its members are so starkly divided.

This is not helped by the fact that corruption is deeply endemic in the Ukrainian government. This is true on both sides of its internal political divide, but the point is that corruption deepens the mutual distrust and suspicion, as well as the overall dysfunction of government.

When Yanukovych fled Ukraine several months ago and the opposition took power, this changed the government's foreign policy orientation but not its corruption or dysfunction, much less the parliament's political polarization. Those problems persisted, and so did Ukraine's internal political instability, so it is unfortunately not shocking that the government has again collapsed.

Who was in the governing coalition that just collapsed?

Since February revolution, Ukraine has been dominated by a coalition of western-leaning political parties. Here are the three largest:

The "Fatherland" party led by Yulia Tymoshenko holds the most seats in parliament and is the leader of the ruling coalition. A mainstream center-right party, Fatherland favors closer integration with with Europe and opposes closer ties to Russia. Tymoshenko is a former prime minister and has unsuccessfully run for president twice, in 2010 and 2014. She was imprisoned by Yanukovych on charges widely perceived to be politically motivated and was released only when he fled the country.

The Ukrainian Democratic Alliance for Reform (UDAR) is a centrist party led by former boxer Vitali Klitschko. UDAR has a somewhat vague political platform that emphasizes good governance and opposition to corruption. Klitschko was originally a presidential candidate in 2014, but he pulled out ahead of the vote and endorsed Petro Poroshenko, who won the election.

Svoboda is a Ukrainian nationalist party that was originally called the Social-National Party of Ukraine. Some people think this was a deliberate reference to the National Socialism of Adolf Hitler. Strongly anti-communist, the party originally limited its membership to ethnic Ukrainians. Svoboda has moderated its image over the last decade, but its politics remain divisive. For example, Human Rights Watch reports that as recently as 2012, a party statement referred to a gay rights protest as a "Sabbath of 50 perverts."

The ruling coalition collapsed because UDAR and Svoboda withdrew their support from the government. Fatherland didn't have enough votes to govern by itself.

Ukraine's polarization makes it particularly difficult for Ukrainian leaders to form a stable coalition. The western-leaning factions already had a relatively narrow majority in parliament, so any disagreements among them was likely to bring down the government, since they were loath to bring Russian-leaning parties into the government. Current polls suggest that fresh elections may increase the majority of the western-leaning parties, which could give their leaders more room to maneuver.

Who are the main opposition parties in parliament right now?

At the start of 2014, the Verkhovna Rada was led by the Party of Regions, which was led by Yanukovych and had won 30 percent of the vote and 40 percent of the seats in parliament. But after Yanukovych fled the country, the party splintered. More than half the Party of Regions legislators quit the party, forming several smaller parties instead. Today, the Party of Regions only has about 80 members in the 450-member body.

Another significant pro-Russian voting block is the Ukrainian Communist Party, which draws a direct line to the Communists who governed Ukraine during the Soviet era. On Thursday, the current pro-Western government sought to ban the Communist Party from parliament for supporting the pro-Russian rebels.

Polls suggest that these parties could see dramatic losses in this fall's election.

Who is Ukraine's president?

The president of Ukraine is Petro Poroshenko, known as the "Chocolate King" for his success in the candy business prior to entering politics. He is worth more than a billion dollars.

Some critics have described Poroshenko as an oligarch

He has traditionally been aligned with the pro-Western parties, but has not been closely aligned with any specific political party. That proved to be an advantage in the May 2014 presidential election, in which he defeated Fatherland's Yulia Tymoshenko, a veteran of Ukrainian politics. Voters found Poroshenko's outsider image appealing.

Some critics have described Poroshenko as an oligarch who used his ties to the government to further his own business interests. Indeed, the US government used to regard him with skepticism. As the Washington Post notes, in 2006 the US ambassador to Ukraine described him as a "disgraced oligarch." In a private diplomatic cable, a US official wrote that "Poroshenko was tainted by credible corruption allegations."

The early parliamentary elections could strengthen Poroshenko's hand politically. While he isn't currently associated with any specific party in parliament, he has organized a Solidarity party that is currently at 23 percent in the polls.

How will the turmoil in parliament affect the Ukrainian civil war and the response to the downing of flight MH17?

It won't help. Under Ukrainian law, an acting government will continue in office until the new parliament is elected. But this acting government will have a serious lame duck problem. It will be unable to make long-term plans that might change in three short months. That will make it harder to deal with the big, underlying issues that predate and help explain the crisis, namely corruption, dysfunction, and a sense of a divided national identity.

The government may also find it even more difficult to approve measures needed to prosecute the war effort against separatist rebels. The government was struggling to pass legislation even before the coalition fell. With an election looming, members of parliament could be even more reluctant to take hard votes that could cost them votes in October. Given that the Ukrainian government increasingly sees itself as at war with Russia — Russia did invade and annex part of Ukrainian territory, after all — this is not a good time for the government to be indecisive.