WASHINGTON (CNN) -- Sen. Barack Obama has missed the most votes of any Democratic presidential hopeful in the Senate over the last two months, including a vote on an Iran resolution he has blasted Sen. Hillary Clinton for supporting.
Sen. Barack Obama makes a campaign stop at Iowa State University on Saturday.
The Illinois Democrat has missed nearly 80 percent of all votes since September.
The other Democrats in the Senate running for president have missed a high percentage of votes as well.
Sen. Joe Biden of Delaware has missed 68 percent of the votes during the same period, Sen. Christopher Dodd of Connecticut 65 percent and Clinton of New York 63 percent.
Obama's campaign points out that Biden missed the most votes if the whole year is considered, followed by Dodd, then Obama.
Obama's campaign argues that looking at the last two months is arbitrary.
Obama missed a vote on a resolution that declared the Iranian Revolutionary Guard, an elite part of the Iranian military, a terrorist organization. He has criticized Clinton for voting for it, saying it would give President Bush a "blank check" to invade Iran.
"This kind of resolution does not send the right signal to the region," Obama said during a presidential debate earlier this week. "It doesn't send the right signal to our allies or our enemies." Watch the report on Obama's voting in the Senate »
Obama was campaigning in New Hampshire when the vote was taken. His campaign blamed his absence on the short notice given when the vote was scheduled. But two senior Democratic Senate aides said senators were advised the night before that the vote would occur the next day.
A spokesman for Obama, however, was adamant Obama did not have enough time to return to Washington for the vote.
Obama has also missed votes on a Democratic priority, the expansion of the federally funded State Children's Health Insurance Program (SCHIP) as well as a vote on a resolution that condemned MoveOn.org for running an ad in the New York Times attacking the top general in Iraq, Gen. David Petraeus.
Most of the votes Obama missed were for amendments to spending bills, when his vote would not have decided the outcome.
Obama's campaign says he was in the Senate for critical votes, and canceled a campaign appearance to be in the Senate for a critical SCHIP vote.
"The most important votes that this Congress did were in the first six months -- ethics reform, minimum wage, Iraq, 9/11 bill, energy," Obama spokesman Bill Burton said. "The last two months have been appropriations bills, and we were here for the Iraq votes."
Stu Rothenberg of the Rothenberg Political Report said the voters may not punish Obama for missing votes.
"I think most Americans understand that if you're running for president, you're going to have to be in Iowa, New Hampshire, and you're not going to make all the votes and they give candidates slack," Rothenberg said.
With the mounting fight with the White House over key bills, Senate Majority Leader Harry Reid is putting all the contenders on notice.
"I am going to leave here and go call our presidentials and let them know that they better look at their schedules, because these are not votes you can miss," Reid said on the Senate floor Friday. E-mail to a friend
CNN's Jessica Yellin and Evan Glass contributed to this report.