The candidate, Mark Gres, was beaten and stabbed in what party officials called an assassination attempt.
Oleksandr Horin, a candidate from the People’s Front Party, led by the prime minister, was savagely beaten the same night after being ambushed in the foyer of his apartment building in Ukraine’s southern Odessa region.
And on Monday, another People’s Front candidate, Volodymyr Borysenko, survived an attempt on his life that included gunfire and a homemade explosive.
Officials said he had survived only because of the body armor he had started wearing after receiving threats.
In the final stretch before parliamentary elections on Sunday, Ukraine’s always rough and unpredictable politics have taken a new and frightening turn.
The attacks have occurred not in the war-stricken east, where government troops have been battling pro-Russian rebels for half a year, but in the heart of the country, in places that for the most part have not directly experienced the fighting.
There was no indication that the attacks were connected, let alone proof that they were politically motivated.
But the spate of violence highlighted the extraordinary tensions surrounding an election that, for better or worse, stands to alter the course of the country by completing the overhaul of the government that began with the ouster of President Viktor F. Yanukovych in February.
The attacks have further marred an election that was already clouded by the expectation that few people in the embattled eastern regions of Donetsk and Luhansk would be able to participate because of continued fighting and rebel opposition.
If the government in Kiev had hoped that parliamentary elections, followed by local elections in December, would help heal the rift in the east as part of a larger effort to grant the area more control, they are now confronted with the reality that rebel leaders plan to block the balloting on Sunday.
They also plan to hold their own elections in November.
Late Tuesday, the authorities said they had arrested a Russian citizen suspected in the attack against Mr. Borysenko, but said no further information would be made public until Wednesday.
And there were warnings of more trouble ahead.
Oleh Lyashko, the flamboyant and provocative leader of the Radical Party, who has been one of the most prominent figures in the election, abruptly canceled all campaign events on Tuesday after the state Security Service warned that there was credible evidence of an imminent assassination attempt.
“We had information that there was an attempted terrorist attack,” said Viacheslav I. Shaposhnik, another Radical Party leader, apologizing to a crowd that was expecting Mr. Lyashko at a rally in the town of Romny.
It was not clear if Mr. Lyashko would appear at any campaign events before Sunday’s vote, which by law will be preceded by a 24-hour quiet period.
In a statement on the Radical Party’s website, he indicated a concern that his campaign rallies could be the targets of an attack.
“According to the information we get from many reliable sources, terrorist acts are being prepared during my parliamentary campaign, which can result in bloodshed and a number of victims among the innocent people who come to these meetings,” Mr. Lyashko said.
The early elections Sunday were called this summer when President Petro O. Poroshenko took steps to dissolve the Parliament, which many Ukrainians viewed as a last vestige of the government of his predecessor, Yanukovych.
Yanukovych’s ouster preceded Russia’s annexation of Crimea and the birth of a Russia-supported secessionist movement in the east that still threatens to tear Ukraine apart.
Fighting has continued despite a truce agreement signed in Minsk, Belarus, in September.
And the authorities in Kiev seem largely powerless to carry out parliamentary votes in the Donetsk and Luhansk regions, which remain partly under the control of the pro-Russian rebels.
In a recent statement, rebel leaders boasted that they controlled more than half of the polling stations in the embattled areas.
Surveys conducted last month suggested that a coalition party led by Mr. Poroshenko and the mayor of Kiev, Vitali Klitschko, had a substantial lead in the race.
An array of other parties are also expected to exceed the threshold needed to form a coalition in Parliament, including the People’s Front Party of Prime Minister Arseniy P. Yatsenyuk and the Radical Party of Mr. Lyashko.
Half of the 450 seats in Parliament are to be filled by direct election.
The other half will be chosen from lists drawn up by each party, with seats apportioned according to the percentage of votes each party receives.
Mr. Yatsenyuk, in a statement on the People’s Front Party website, said he was certain the attack on Mr. Borysenko had been politically motivated and demanded that the assailants be found.
“I think this is exclusively connected with his political actions,” Mr. Yatsenyuk said.
Mr. Gres, the Radical Party candidate who was stabbed, said the attack on him might have been connected to his criticism of the leader of a volunteer battalion fighting pro-Russian rebels in the east, which, if true, underscores the internecine rivalries that exist even among groups united in their opposition to the insurrection.
A separate fight has emerged between the Kiev government and rebel leaders over the scheduling of local elections.
In a law granting “special status” to Donetsk and Luhansk, Parliament had agreed that the two regions could choose their own local officials, but said they would do so on Dec. 7, the same day as other regions throughout Ukraine.
Rebel leaders, however, have said they will hold their own elections on Nov. 9.
Source: The New York Times