But the United Auto Workers, which Nader mentioned in his speech, and other groups that endorsed Obama said they support Obama because of his platform, not his party.
In a statement, Ron Gettelfinger, UAW president, said the union's International Executive Board voted to endorse Obama because he has said he wants to work on behalf of working families. The issues of the election made it clear to the board whom they should support, he said.
"Barack Obama is a progressive leader who supports the UAW agenda: quality affordable health care for all, the right to join a union without employer interference and a renewal of American manufacturing," Gettelfinger said.
The American Small Business League also supports Obama, said spokesman Chris Gunn.
When Obama said he wants to stop diverting government contracts from small businesses to large businesses, Gunn said that issue swayed the organization to support him. League officials said they did not know where Nader stood on the issue, so they could not endorse him, Gunn said.
"The endorsement was not because he was the Democratic candidate," Gunn said. "We're here for small businesses."
Both major parties have strong support from corporations, but Gunn said he hopes Obama will also protect small business interests.
From his campaign donations, Nader said he thinks Obama is corporate America's candidate. Obama has received more donations from corporate interests than Republican candidate John McCain, and Nader said liberals have ignored this.
"The liberal intelligentsia is so determined to not have a repeat Bush clone that they will give him a free ride," he said.
Nader is listed on the ballot in 45 states. In the polls where he is included, 5 to 8 percent of voters say they will vote for him. Nader is not on the ballot in Oklahoma, Texas, Georgia, Indiana and North Carolina.
For the system to change away from just two political parties, Nader said it will take an extremely strong grassroots effort or a billionaire who wants to run for president and can toss enough money into the race to get attention as a viable third party candidate.
He said he hopes people will eventually get used to the idea of seeing more than two candidates.
To make it work, he said the Electoral College should be abolished, public financing for campaigns should be restructured and ballot access should be easier for candidates.
For a system that greatly protects voters' rights, "they don't pay much attention to candidates' rights," Nader said.
On Saturday, he will break a record for the most speeches in a day during his Massachusetts marathon. Nader said he plans to give 21 speeches in 21 towns and cities to take his campaign to the voters and the local media.
The mainstream media has mostly ignored his campaign, he said, with one story in the New York Times, two in the Washington Post and very few mentions on television news shows.
The lack of attention because he is not a major candidate turns into a downward spiral because he said he cannot be a major contender unless people know about him. Nader said he wishes he could have at least participated in the presidential debates.
"If we were at the debates, I think we would have been in a three-way race," he said.