SIMI VALLEY, California (CNN) -- Republican presidential hopefuls will face off Wednesday night without a familiar face now that former New York Mayor Rudy Giuliani has dropped out.
Ex-New York Mayor Rudy Giuliani, here with his wife, Judith, is expected to end his White House bid.
The remaining candidates will take the stage in a debate -- sponsored by CNN, the Los Angeles Times and Politico -- beginning at 8 p.m. ET Wednesday.
The event at the Ronald Reagan Presidential Library in Simi Valley, California, follows Arizona Sen. John McCain's Tuesday night win in the Florida primary.
McCain topped former Massachusetts Gov. Mitt Romney 36 percent to 31 percent in the hotly contested race.
Giuliani ended his White House bid and endorsed McCain at a the Reagan library on Wednesday.
"This is a man who is prepared to be president," Giuliani said of his "old friend."
Giuliani said McCain gives the Republican Party its best chance to hold onto the presidency.
The debate will now be a four-candidate affair -- McCain, Romney, Huckabee and Paul -- with CNN's Anderson Cooper moderating. Watch a preview of what to expect at the GOP debate »
A spirited exchange over the economy will likely take center stage. The economy was by far the No. 1 issue for Florida voters Tuesday, according to exit polls. Forty-five percent of Florida Republicans surveyed after voting said the economy was the most important factor in their choice for president.
Wednesday night's event is expected to be the last face-to-face showdown between the Republicans before next week's Super Tuesday contests in which 20-plus states will hold primaries and caucuses.
In many of those states, delegates will be on a "winner take all" basis so the stakes couldn't be higher as the candidates debate alongside a retired Air Force One at the Reagan library, a site considered sacred ground for Republicans.
In his victory speech Tuesday night in Florida, McCain evoked the 40th president, saying, "Our party has always been successful when we have, like Ronald Reagan, stood fast by our convictions."
With wins in New Hampshire, South Carolina and Florida, McCain has emerged as the GOP front-runner, possibly the first time this primary season that a candidate could make that claim. Watch how McCain won in Florida »
But the four-term senator, who cultivates an image as a maverick, still must work to convince the GOP's conservative base to back him. Many conservatives vilify McCain for breaking with them on immigration, campaign finance, taxes and other issues.
"Our victory might not have reached landslide proportions, but it is sweet nonetheless," McCain told supporters in Miami. "My friends, in one week we will have as close to a national primary as we've ever had in this country. I intend to win it and be the nominee of our party."
Bad blood between McCain and Romney could bleed over into Wednesday's debate.
Last week's Republican presidential debate in Florida was a civil affair, but hours afterward, attacks and counterattacks between the two candidates and their campaigns broke out. Watch a time-lapse video as the debate stage is built »
Since Friday, the two sides have fired away at each other over the Iraq war, the economy, illegal immigration and border security, campaign finance reform and the environment -- each accusing the other of pursuing "liberal" policies.
Romney took aim at McCain on Tuesday night, putting his opponent on the hot seat for failures in Washington, his criticisms of President Bush and his move directly from the military into Congress.
Speaking to supporters after conceding Florida, Romney accused his opponent of being a Washington insider. "Washington is fundamentally broken. And we're not going to change Washington by sending the same people back, just to sit in different chairs," he said. E-mail to a friend
CNN's Paul Steinhauser contributed to this report.