Make use of the article to answer the questions.

Mexico City (CNN) -- Hours after Mexico's presumed president-elect, Enrique Pena Nieto, said it was time for his country to leave behind the political rancor of campaign season, his closest opponent in the polls refused to concede and said the vote had been "plagued by irregularities."

Andres Manuel Lopez Obrador, who election authorities projected as the runner-up in Sunday's presidential vote, said Monday that he was awaiting the official election results, and prepared to contest them before judicial authorities if they didn't turn out in his favor.

"The election was plagued by irregularities before, during and after the process," said Lopez Obrador.

The Democratic Revolution Party candidate's declarations echoed comments he made in 2006, when election authorities said the leftist candidate narrowly lost the presidential race to Felipe Calderon. Lopez Obrador claimed election fraud and never conceded, referring to himself afterward as "the legitimate president of Mexico."

His supporters protested nationwide. In Mexico City, they staged sit-ins and blockades.

On Monday, Lopez Obrador called on his supporters to wait for the official results. The Federal Election Institute's verification of individual poll results begins Wednesday.

Earlier, Pena Nieto, who election authorities projected as the winner of Sunday's presidential vote, told CNN en Espanol he was ready to work across party lines to build a better Mexico.

"We have to be constructive and put aside our differences, which are only for competitions and electoral contests," Pena Nieto said Monday. "Yesterday I indicated that (after) this tense and divisive atmosphere, which is natural in all democratic contests, we have to turn the page and move on to enter another chapter, another moment in our political lives, with a willingness and spirit that are constructive and purposeful."

1. Who protested?
2. What did they do in Mexico City?

Numbered answers:
1. His supporters
2. staged sit-ins and blockades.