Tonight's headliners are Sen. Joseph Lieberman, an independent and onetime Democratic vice presidential candidate, and Fred Thompson, the former senator and "Law and Order" star who abandoned his own presidential bid. The keynote address by Rudy Giuliani, another vanquished McCain rival, was originally scheduled for tonight but has been pushed back to an undetermined night.
Watch ABC's George Stephanopoulos' exclusive interview with Barack Obama this Sunday on 'This Week with George Stephanopoulos'
On Monday Palin rocked the Republican convention when she released this statement:
"Our beautiful daughter Bristol came to us with news that as parents we knew would make her grow up faster than we had ever planned. We're proud of Bristol's decision to have her baby and even prouder to become grandparents," read a statement released Monday by Sarah Palin, and her husband, Todd.
"If Democrats try to attack, it will backfire spectacularly," a McCain campaign official told George Stephanopoulos.
McCain campaign senior adviser Nicolle Wallace said that laying off a candidate's children had been the "last really civil tradition of politics" but that had been violated by the "lewd and outrageously false rumors" being pushed by "Democratic leaning blogs."
Those rumors claimed that Palin's 4-month-old son, Trig, was actually her grandson and Bristol was the true mother. Wallace said the family decided to end those rumors by announcing Bristol's pregnancy, she said.
Wallace also said the pregnancy was not a surprise to McCain or his team that vetted Palin's VP candidacy.
"It was certainly known, and it didn't give Sen. McCain any pause, and I don't think it will give the American people pause that this is a real family dealing with real issues," Wallace said.
On the convention floor, delegates opposed to abortion rights agreed with the Palin family decision to keep the baby.
"It energizes us, because she's standing on our principles, of every life is precious," said Terris Louis Gregory, a Kansas delegate.
"I'm pleased and appreciative of the fact the girl is not going to kill her baby and instead she is going to marry the boyfriend, and I like that and appreciate that," said Michael Bergsma, a Texas delegate.
Wearing a button with flashing red lights that reads "the LIFE of the party, Republican National Convention 2008" Donna Crocker, 69, a Texas delegate, said it's good Palin came out early with the revelation.
"I think the fact that Palin's out in front with it is really a very good thing. My prayers are with the family," Crocker said. "The fact that her daughter's keeping it and marrying the father is wonderful. It's a human life and she is respecting that."
Ironically, perhaps, one of the strongest statement came from Democratic presidential nominee Barack Obama.
"You know my mother had me when she was 18, and how a family deals with issues and, you know, teenage children, that shouldn't be the topic of our politics, and I hope that anybody who is supporting me understands that's off limits," Obama said.
The pregnancy surprise jolted an already radically different convention than the one that had been planned.
First lady Laura Bush and Cindy McCain addressed delegates at the end of a truncated perfunctory convention session Monday afternoon.