Prime Minister Viktor Yanukovych has the support of 34 percent of respondents, while Viktor Yushchenko, a former prime minister and the leader of the biggest opposition coalition, Our Ukraine, has almost 32 percent.
Their closest competitors are Socialist Party candidate Oleksandr Moroz, who is trailing far behind with about 5 percent, and Communist Party candidate Petro Symonenko, with 3.4 percent. The other 22 candidates together received just 3 percent support.
Yanukovych has pushed ahead for the first time since campaigning began. Natalya Pohorilka, the director of the Socis-Gallup polling firm, told RFE/RL: "In the last two weeks, Yushchenko's ratings have fallen by two [percentage points] while Yanukovych's have risen by six. At what cost? Foremost, the ratings of [Communist candidate] Petro Symonenko and [Socialist candidate] Oleksandr Moroz have fallen."
Around 20 percent of the electorate is undecided or did not state a preference.
The director of the Democratic Initiatives think tank, Ilko Kucheriv, attributes part of the advance by Yanukovych to Yushchenko's absence from the campaign trail for most of the last month because of a serious illness, which his supporters claim was caused by poisoning. He also notes that Yanukovych doubled pensions last month.
The Russian language has been an important issue in the campaign. Yanukovych is seen as pro-Russian and has advocated introducing dual citizenship and Russian as a second state language. Both of these measures appeal to Ukraine's large ethnic Russian and Russian-speaking populations, who comprise up to 20 percent of Ukraine's 48 million people.
Yanukovych portrays Yushchenko's Our Ukraine faction as promoting the interests of Ukrainian-language speakers, most of whom are from western Ukraine.
Both candidates promise to improve Ukraine's economy and to raise salaries for public-sector employees. Yanukovych says he is not turning his back on the West and the European Union but repeatedly advocates strengthening economic and political ties with Moscow.
Yushchenko says his country should have good relations with Moscow but wants Ukraine to join the European Union and NATO.
As the election draws near, supporters of both leading candidates are accusing the other side of using dirty tricks.
Yushchenko's aides cite numerous examples of the government using its powers to unfairly influence the campaign, including overwhelming exposure given to Yanukovych by the country's mass media, which is mostly either government-controlled or owned by government supporters. The opposition also claims that the government intends to rig the vote or may cancel the results if Yanukovych loses.
Meanwhile, an explosion ripped through the offices of Prosvita, a pro-opposition group in the western city of Lviv early today. No one was injured.
Yanukovych's supporters accuse the opposition of planning to use violence if their candidate loses. The Kyiv headquarters of the Ukrainian Party of Regions, led by Yanukovych, was reportedly attacked on 16 October by around 15 people. A guard was injured and furniture and office equipment were broken. Yanukovych supporters also attribute a bomb blast that damaged a commercial building in the city on 17 October to Yushchenko supporters.
Police have said a raid last weekend on the offices of a pro-opposition group called Pora turned up a grenade and other explosives. Prosecutors say a terrorism investigation has been launched against five members of Pora. Members of Pora say the items were planted by the police.
After the attack on their office, a spokesman for the Party of the Regions, Hennadiy Samofilov, blamed opposition sympathizers and warned of the possibility of future violence.
"I consider today [that the blame lies with] the consistent behavior of certain political forces," Samofilov said. "We see in these last 13 years who occupied the offices of the Communist Party? Who attempted to occupy the offices of the presidential administration? Who occupied the parliamentary chamber? These are precisely the forms and methods of a fight for power. I think these are the conclusions we should make from these facts. It's escalating. Yesterday, there were explosives. And what will tomorrow bring -- the start of the shooting?"
Yushchenko returned to active campaigning last week. On 16 October, he addressed a rally of some 10,000 student supporters in Kyiv. He appeared physically strong but his face was still disfigured by illness. He said he is confident of victory and urged his supporters not to pay attention to polls.
"I'm giving you my word that if just one cell in my body doubted that we will together claim victory on 31 October, then I wouldn't be standing here on this podium before you. But I'm here because I believe in you, I know what to do, and I believe in Ukraine," Yushchenko said.
A sociologist from the Democratic Initiatives think tank, Iryna Bekeshchyna, told RFE/RL that surveys show the majority of the electorate believes the election campaign has been unfairly skewed in Yanukovych's favor.
"The election campaign has been regarded as unfair and dishonest by the majority of voters, and just as they did not previously believe in the fairness and honesty of the ballot count, as they did not believe that the television channels and mass media have reported fairly on the campaign and that one candidate [Yanukovych] is given all the advantages and the others are not given a chance to communicate with the electorate, that remains the way they view the situation," Bekeshchyna said.
Student leaders addressing the 16 October opposition rally in Kyiv claimed that police tried to prevent many buses carrying students from proceeding and had succeeded in some cases. They pledged mass demonstrations in case of election fraud.
[For full coverage of the run-up to Ukraine's presidential elections, see RFE/RL's webpage on Ukraine.]