The Republicans have held the White House for 28 of the last 40 years. While there are many reasons for their success, it has a lot to do with forgiving and forgetting once a nominee is chosen.

In 2000, Sen. John McCain and George Bush were duking it in the South Carolina primary as part of the battle for the Republican party's presidential nomination.

To illustrate the nastiness of that fight, a whisper campaign pushed the rumour that McCain had fathered a black baby out of wedlock (he has an adopted daughter from Bangladesh). At the time, South Carolina's state legislature was still flying the Confederate flag.

McCain lost that primary and would ultimately lose the nomination. McCain, a former military man, proved a good soldier once again and actively supported Bush's presidential campaign. Bush, now winding down his second term, has promised to help McCain.

There's a lesson there for the Democratic party, journalist, author and CNN contributor Roland Martin told CTV Newsnet. Republicans set aside their differences for the greater good. "That's one thing the Republicans do that Democrats don't do," Martin said.

Former McCain rival Mitt Romney, who is considered a possible vice-presidential nominee, has been in Denver attacking Obama. So has former New York mayor Rudy Giuliani, another also-ran for the Republican nomination.

"The Republicans have an Al Davis 'just win, baby' philosophy," Martin said, referring to the owner of the NFL's Oakland Raiders. "The Democrats, unfortunately, want to hold grudges. You want to hold a grudge, you don't win the White House."

Hillary Clinton and Barack Obama went through a bruising, seven-month, 50-state battle before the first-term Illinois senator emerged with a narrow win. He is the first African-American to win a major party's nomination for the presidency. Hillary's supporters are disappointed, with up to one-quarter of saying they will vote for McCain. And her husband Bill, a two-term Democratic president, has been visibly upset at the convention.

If Bill Clinton wants the Democrats to win on Nov. 4, he needs to deliver the following message: "It's not about me, it's not about my wife. It's about this party taking back the White House."

Democrats must be more forceful in making the case about the stakes in this election, Martin said.

"Sitting on the sidelines, saying you're going to support McCain because you're ticked off? Then you better shut up for the next four years, because you were part of the problem," he said.

Renan Levine, a University of Toronto political scientist, believes hardcore Clinton supporters will fall into line after the speech to the convention Tuesday night.

"I expect that the vast majority of the activists that supported her will back Obama for many of the reasons she described last night," Levine told CTV.ca. "They may not love Obama, but the idea of four more years of Republican rule will be largely repugnant to them."

Patrick Basham, director of the Democracy Institute, told CTV Newsnet that the latest polls show that conservative Democrats who flocked to Clinton are continuing to trend to McCain.

"It's too early to say whether (Hillary's) speech failed, but the early indications are that it didn't succeed" in bringing those Democrats home to Obama, Basham said.