(CNN) -- Republicans briefly stopped attacking Sen. Barack Obama for what they call his lack of foreign policy experience to note the historic significance of the United States nominating the first African-American for president.
Ex-New York Mayor Rudolph Giuliani, with other Republicans, says Obama is not qualified to be president.
"It's a tremendous night for America," said Ed Rollins, a Republican campaign consultant who has worked on high-profile political campaigns including Gov. Mike Huckabee's 2008 presidential bid.
"We're in a real close, real tight race. And this guy has a real shot at winning. At the end of the day, this is an extraordinary candidate," he said.
"We can all share in how far we've come," said CNN conservative political analyst Amy Holmes, who is African-American.
But the warm fuzzies from the GOP ended after former President Bill Clinton took the stage Wednesday at the Democratic National Convention in Denver, Colorado.
Clinton declared Obama "ready to be president of the United States." To wild applause, Clinton reminded his audience that when he ran for president in 1992, critics said he was too young and inexperienced to lead the nation.
"It didn't work in 1992 because we were on the right side of history and it will not work in 2008 because Barack Obama is on the right side of history," Clinton told the cheering crowd. Watch Clinton's entire speech »
Clinton's comments raised typical reactions from Republicans, who say voters are facing the choice between a candidate with decades of experience in government and another with just a few years of service.
Rep. Christopher Shays of Connecticut said the circumstances of past campaigns were irrelevant and accused Clinton of wrongly taking credit for the economic prosperity that marked his presidency.
"Bill Clinton ran against George Bush Sr. Barack Obama is running against John McCain and that's a big difference," Shay said.
"In my view, a new Republican majority in 1994 saved the Clinton presidency," he said. "We balanced the federal budget. We were the ones that cut spending."
Ralph Reed, a former senior adviser to George W. Bush's campaigns in 2000 and 2004, said Clinton's speech was big on rhetoric, but failed to hammer down key issues for the American people.
"I found it ironic that Bill Clinton, who vetoed $500 child tax credit and vetoed welfare reform, our most successful reform, twice before signing it, is criticizing John McCain, who is proposing taking child tax credit and doubling it," Reed told CNN's Larry King.
"Bill Clinton is one of the supreme political talents, but he's both a blessing and a burden," said Reed, noting Clinton's speeches at the past two Democratic conventions.
The Republicans pounced on Clinton's about-face on Obama's experience.
"After three full days of the Democratic National Convention, President Clinton was finally forced to testify that Sen. Obama is ready to be president, despite his previous arguments to the contrary," said Tucker Bounds, a spokesman for Republican candidate John McCain.
Republicans also dismissed a speech from vice presidential candidate Sen. Joe Biden, who criticized McCain's support of offshore drilling.
"Joe Biden's argument was more of the same," said radio host Lars Larson, echoing Biden's refrain that a McCain presidency would be "more of the same" from the Bush administration. "It was a tired speech." Watch Biden's entire speech »
Ultimately, the Republicans agreed that the election's outcome hinged on the candidates' policies and not charisma on display by Clinton or Obama, who surprised the crowd by appearing at the end of Wednesday's convention.
"It played exactly into the critique that the McCain camp has set up, that Barack Obama is this celebrity. He makes this celebrity entrance at the end night and offers no substance," GOP strategist Kevin Madden told CNN's Larry King.
"It's a lot of talk, a lot of rhetoric but it's like cotton candy -- it melts on contact but you can't live on it," he said.
Earlier Wednesday, former New York Mayor Rudolph Giuliani, who ran for president as a Republican, used the Clintons' own words to cast doubt on Obama's qualifications.
Giuliani evoked the infamous "3 a.m." moment during the primary season, when Hillary Clinton ran an ad asking voters who they wanted to respond to notification of a crisis at an unexpected moment.
Former U.S. treasurer Rosario Marin criticized Obama for not mentioning the name of any Latin American countries when Obama addressed a crowd in Berlin, Germany, this summer.
"I was not just disappointed, but rather, I was insulted," Marin said.
The Republican Party set up a war room down the street from the convention, staffed by volunteers busily chatting on their phones and hammering away on laptops opposing much of what the Democrats say.
Standing next to two big dry-erase boards and television monitors, a young McCain supporter instructed a table of volunteers in their latest spin about "solving problems."
"The fact is," Matt McDonald said, "Obama has no record whatsoever doing that, and John McCain has a long record of doing that, so that should be at the core of the response."