The lineup for the CNN Republican debate features nine candidates, including U.S. Senator Marco Rubio, left, businessman Donald Trump, center, and retired neurosurgeon Dr. Ben Carson, who are shown standing prior to the start of the 2016 U.S. Republican presidential candidates debate held by CNBC in Boulder, Colorado, Oct. 28, 2015. Reuters/Rick Wilking

Familiar faces, and at least one recognizable and distinct hairdo, will grace the stage Tuesday night for the fifth Republican presidential debate, held in Las Vegas and hosted by CNN, but can any of the candidates be expected to offer new information for viewers? Here are key things to know about the Republican White House hopefuls who will face off tonight in two different sets.

The lineup for the primetime debate, which is scheduled to start at 8:30 p.m. EST, features businessman Donald Trump, retired neurosurgeon Dr. Ben Carson, Florida Sen. Marco Rubio, Texas Sen. Ted Cruz, Ohio Gov. John Kasich, New Jersey Gov. Chris Christie, former Florida Gov. Jeb Bush, Kentucky Sen. Rand Paul and former Hewlett-Packard CEO Carly Fiorina. They garnered spots on the stage by polling with at least 3.5 percent support nationally or 4 percent support in Iowa or New Hampshire. CNN political anchor Wolf Blitzer is due to moderate.

Trump was expected to take the center podium, flanked by Carson on his right and Cruz on his left. Christie was expected to make his return to the primetime slot after gaining support in New Hampshire. He was relegated to the undercard debate for November's Fox Business set. Meanwhile, Paul barely made the cut for the main stage, but polling Sunday showed he had enough support in Iowa to be included.

Four Republican debates have come and gone, and candidates' fortunes have waxed and waned in between. Tonight, it's a recent surge in support for Cruz that has caught analysts' attention. Recent polling shows that in Iowa, Cruz has gained the lead over Trump. Cruz has 31 percent, compared to Trump's 21 percent. Going into the most recent GOP debate, it was a surge in polling by Carson that drew attention, although support for him has faded in recent weeks.

This time, it's Cruz's ascent that has raised questions about the senator's acceptability among the GOP establishment, especially in light of Trump's sustained run and seemingly unassailable position at the top of the polls. Cruz himself has espoused views that the traditionally conservative GOP has found to be extreme, and since he announced his candidacy in March, analysts have cast him as being far too ideologically to the right to win the nomination. But he may look different now, in light of Trump.

Asked if he preferred Cruz to Trump, Republican lobbyist Ed Rogers told CNN, "Oh God, yes." He added, "Compared to Trump, he's OK."

Strategists will therefore be watching Cruz, although they'll also have their eyes on Rubio, to see if a figure more representative of the GOP establishment will stand out this time around.

The undercard debate, slated for 6 p.m. EST, includes former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum, South Carolina Sen. Lindsey Graham and former New York Gov. George Pataki.