Many Ukrainians say they regard the country’s political leaders since the end of the Soviet era to be a collective failure. At the same time, they say they recognize the constraints of being almost entirely dependent on Russia for energy, especially natural gas for heat, as well as the historic burden of being home to vital Russian military assets, including major installations for its Black Sea fleet.

“The foundation has to be completely changed in our country, so that it would not remain a post-Soviet barrack temporarily repainted in yellow and blue,” Mr. Lutsenko told the crowd, referring to the colors of the country’s flag. “We have to understand that not only the president has to be changed but the entire system.”

Mr. Lutsenko knows the perils of the system well. From his role as field commander, he went on to serve as a leader in Parliament and as the interior minister, under President Viktor A. Yushchenko, who was poisoned by dioxin in an assassination attempt during the disputed 2004 election. After Viktor F. Yanukovich, the revolution’s antihero, won the presidency in 2010, Mr. Lutsenko was arrested and jailed on abuse of authority charges, only to be pardoned earlier this year as Mr. Yanukovich came under pressure from the West.

Supporters of European integration had been pinning their hopes on the political and trade agreements, which had been in the works for more than four years, and Mr. Yanukovich had long talked about signing them at a major conference that begins on Thursday in Vilnius, Lithuania.

In contrast with 2004, they say they are focused entirely on raising standards of living, and putting Ukraine on track to become a member of the European Union so they could obtain the benefits that they see are now enjoyed by neighboring Poland and by the fellow ex-Soviet republics in the Baltics.

“I want to live in a country where the law is not just a word in the dictionary,” said Kateryna Zhemchuzhnykova, 25, a journalist who has been leading protests in the city of Donetsk in the traditionally Russia-friendly eastern half of Ukraine. She said she wanted a country “where people are free to tell what they think; to do what they want; to go where they dream.”

Ms. Zhemchuzhnykova said that while her demonstrations had been relatively small, numbering 150 to 200 people each evening, and that protesters had faced some heckling, there had been no rallies in Donetsk in opposition to the accords with the European Union.