Marko Djurica / Reuters

Voters in the U.K. are deciding Thursday the composition of their Parliament, a pivotal choice that will determine who forms the next government.

Most polls suggest the center-right Conservatives, headed by Prime Minister Theresa May, will emerge the biggest party, though its 21-point lead over the opposition center-left Labour Party has fallen in the run up to the June 8 vote. Still, the Tories, as the Conservatives are known, are expected to have enough seats in the 650-seat House of Commons to form a new government; 326 seats are needed for a majority. (In the U.K.’s parliamentary system of government, the leader of the ruling party is invited to head the government, as prime minister.)   

It’s worth noting, however, that the polls in the U.K. have been unreliable in recent races. Most polls predicted a tight race ahead of the Scottish independence referendum in 2014: but the “No” vote won by about 55 percent to 45 percent. Then in the previous general election in 2015, polls showed the race was too close to call, but the Tories, then headed by David Cameron, emerged with a slim majority in Parliament. Ahead of the Brexit referendum last year, polls showed the “Leave” vote leading, but within the margin of error. (Leave won 52 percent to Remain’s 48 percent.)

The specter of terrorism and Brexit loom over Thursday’s vote. This year alone, Islamist extremists have attacked London twice and Manchester once, killing 35 people in total. Critics of May, including Jeremy Corbyn, the leader of the Labour Party, and the police federation have blamed, in part, a lack of police personnel for the attacks. They say that many of the cuts faced by the police were put in place by David Cameron’s government when May was home secretary, overseeing, among other things, police budgets. Indeed, more than 20,000 police jobs were cut in the six years during May’s time as home secretary. It’s also true that crime fell during May’s tenure, but it’s hard to point that out amid three terrorist attacks in a space of 11 weeks—especially now that she’s running the country.

May was also criticized—and not just by her critics on the left—for her remarks after the June 7 attack in London that there’s “far too much tolerance of extremism in our country.” Many Britons pointed out that her approach to radicalism in the U.K. schools in 2014 was described by then Education Secretary Michael Gove as waiting for “the crocodiles to reach the boat.” Gove had wanted instead to, in his words, “drain the swamp.”

Then there’s Brexit: The decision to leave the EU was supposed to dominate the election. May has promised to be a “bloody difficult woman” during the negotiations with the EU. As Ian Dunt wrote in The Atlantic: When “May triggered the election, [she hoped] … to significantly expand her slim 17-seat majority. Her proposition was simple: Who would you prefer in the negotiating room: Corbyn or her? May was confident the public would go for the latter. But things did not go quite as she expected.”

Indeed, there were problems with other policy issues, as well. As Samuel Earle noted in The Atlantic:

It started with what many saw as her first campaign policy: an absurd declaration to bring back fox-hunting, revoking a ban on foxes being devoured by dogs that eight out of 10 Brits were said to support keeping in place. Soon followed a U-turn on an unpopular manifesto pledge, dubbed the “Dementia Tax.” The plan was to make seniors pay means-tested contributions towards their own social care—not entirely unreasonable—but without any cap on how much they might have to spend. May swiftly backtracked on the latter part, vaguely alluding to the fact that a cap would be introduced. The press lapped it up: It was framed as the first time a party had reversed on a manifesto policy before an election.

In any other circumstances, May should be nervous about Thursday’s election, but she’s facing Corbyn, whose massive popularity among Labour’s rank and file is matched only by his unpopularity among the wider British public. Corbyn was praised for his strong remarks after the terrorist attacks, but also criticized for politicizing the attacks by referring to the massive police cuts during May’s tenure as home secretary. Under a Labour government, he said, “there will be more police on the streets”—not something you’d typically expect a left-wing politician to advertise. Corbyn also linked U.K. involvement in foreign wars with terrorism at home—a view that polls suggest resonates with a majority of Britons, both on the left and the right. But Corbyn, has in the past, been criticized for being soft on terrorism (he once said he favors talks with his “friends” in Hamas and Hezbollah), and his hard-left prescriptions for the U.K. are viewed by many of his critics—not least among them members of the center-left of his own party—as a return to the old left-wing policies of the 1980s and before.

Those are the two major choices Britons face as they vote Thursday. Results should be known early Friday.

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