HOUSTON — For Marco Rubio and Ted Cruz, this might be their last, best chance.

The final Republican presidential debate Thursday night before the Super Tuesday contests has the potential to be an epic display of anger and rhetorical aggression, with Rubio and Cruz going after each other on everything from policy to character as each struggles to emerge as the single alternative to Donald Trump.

At this critical juncture in the race, with Trump on a three-state win streak and Republican operatives questioning whether time is running out to stop the New York billionaire, tonight's fireworks-filled forum will provide a window into the contenders' end-game strategies.

Here's what POLITICO is watching in Thursday's GOP debate.

Rubio's playbook

Rubio has yet to aggressively engage Trump — and those briefed on his strategy say he's unlikely to do so on Thursday night.

The Florida senator has concluded that going after Trump would accomplish little because the businessman's supporters are deeply committed and unlikely to swing Rubio's way. Inciting a confrontation with Trump onstage would create drama but wouldn't help the senator gain voters, something he badly needs as he looks for his first primary win.

Instead, Rubio's team has decided his best bet is to focus fire on Cruz. They think the Texas senator's voters are less locked in and could swing Rubio's way should Cruz fade. The only way to dislodge Trump, Rubio's advisers say, is to turn it into a two-man race — meaning that they first need to get Cruz out of the way.

Of course, if Trump chooses to engage Rubio — something he hasn't yet done in a debate — Rubio will have to respond. And while Rubio may not directly take on Trump, he may do so implicitly.

Rubio will also be playing to the more mainstream, establishment Republican donors and supporters, arguing as he has shown in recent days that he is the only candidate who can unite the party and win the general election.