When Yushchenko himself was asked, in an interview earlier this month with the Russian newspaper Izvestia, whether Yanukovych and current President Leonid Kuchma could be behind the poisoning, his response was not direct.
"The authorities know they cannot win the election straightforwardly," he said. "As for the incident you refer to, no comment. I know what kind of country I live in, with what kind of prosecutor general in office. I will acquaint journalists with all the results of the medical tests and examinations. I'm convinced it will shed light on the matter."
The contest is often painted as one between a pro-Western reformer who would bring Ukraine closer to the United States and Europe (Yushchenko), and a neo-Soviet leader who would pull the country away from the West and closer to Russia (Yanukovych). But nothing is quite that simple.
Yushchenko has been portrayed by his opponents in the campaign as both a U.S. puppet and a kind of neo-Nazi who would repress Ukraine's large ethnic Russian minority. Yushchenko himself has spoken of the need to eliminate corruption, strengthen democratic principles such as freedom of the press and foster better relations with the West, but he also said he would withdraw all Ukrainian troops from Iraq, saying the country has no reason to be there.
Some Ukrainian scholars said the country is in a state similar to that in the Soviet Union in the late 1980s.
"Those in power are really panicking, but they can't control the society and they really feel that they can lose," Yaroslav Hrytsak, a visiting professor of political science at Columbia University from Lviv University in Ukraine told ABCNews.com. "But I believe they are not as strong as they pretend to be."
"If Viktor Yushchenko is to be elected in the second round, this would in effect be a democratic revolution to complement Ukraine's national revolution that took place in 1991," Kuzio said.
Yanukovych was handpicked by the current president, after Kuchma was unable to get the legislature to approve any of his proposed constitutional changes that would have allowed him to stay in power when his second term runs out.
Yanukovych has presented himself as a leader who would be able to strengthen relations with the United States while maintaining Ukraine's ties with Russia, and a man with the will and ability to control corruption in a country where it is estimated more than 50 percent of the economy is black market.
"If you don't know him, if you don't know his biography, he looks OK, he looks pretty good," Hrytsak said.
He reportedly twice spent time in Soviet prisons for violent crimes, and a former major in the Security Service of Ukraine, Mykola Melnychenko, turned over to the Ukrainian parliament tapes he said implicated Yanukovych in corruption.
The tapes, allegedly made in Kuchma's office, contain voices that sound like Kuchma's and Yanukovych's discussing bribing members of parliament, using violence and other means to suppress freedom of the press, and controlling independent businessmen.
And his claim that he supports good relations with the United States is suspect, Kuzio said, because other candidates the scholar said were directed by Yanukovych ran vicious anti-American campaigns as a way of mobilizing opinion against Yushchenko.