Washington (CNN) It's a week away from Super Tuesday -- but tonight is a big evening for politics, too.

The menu for politics lovers starts with a Democratic town hall featuring Hillary Clinton and Bernie Sanders on CNN at 8 p.m. ET.

Then come the results from the Nevada Republican caucuses, where Donald Trump, Florida Sen. Marco Rubio and Texas Sen. Ted Cruz will battle it out for first place in the last GOP election before 12 states vote next Tuesday.

Here's what to watch on an important night for both parties:

Clinton's Wall Street wobbles

Democrats have already held their caucuses in Nevada and Clinton snatched momentum there against Sanders. The challenge for Clinton is to keep it going.

In the days since her Nevada victory, Sanders has increasingly sharpened his attacks on Clinton. He picked up on an issue he'd previously dropped, with his campaign tweeting Monday about Clinton's refusal to release her paid speeches to firms like Goldman Sachs: "It's been 17 days, 16 hours and 32 minutes since @HillaryClinton said she would 'look into' releasing her paid speeches to Wall Street."

Clinton still doesn't have a good answer to questions about why she gave speeches to the Wall Street firms she now says she'll be tough on -- and why she won't release the transcripts of those speeches.

It's among the reasons exit polls show Sanders continuing to trounce Clinton on the issue of credibility.

She stumbled on the issue during the last CNN Democratic town hall. Tuesday night's forum could show whether she has found a better way to answer those questions.

Sanders courts blacks

The Democratic contest in South Carolina on Saturday is all about African-American votes -- and whether Sanders, who looks all but certain to lose there, can gain enough ground to turn states with similar demographics competitive in the future.

But Sanders' message is sometimes discordant.

In an interview with BET that aired over the weekend, he accused Clinton of pandering to the African-American community by cozying up to President Barack Obama on issue after issue.

Then, Sunday night, he went to a Baptist church in West Columbia and praised Obama's legacy -- particularly the economic recovery.

He'll have to strike the right tone to make South Carolina competitive -- -- as well as southern states such as Texas, Georgia and Virginia that vote on Super Tuesday.

The key for Sanders: Connecting his core message about economic inequality to the concerns of the African-American community, under pressure from Clinton, who has portrayed him as failing to address other forms of discrimination.

Will the Trump train gain steam?

It sounds like a scene out of a movie: The billionaire Trump, on stage at The Nugget Casino Resort in Las Vegas, celebrating a campaign victory.

If that's how Tuesday night plays out at the Nevada caucuses, it'll leave Trump with three firsts and one second-place finish through the four early states -- enough that, any other year, would leave him looking set to run away with the nomination.

He still faces some challenges.

So far, Trump has benefitted from a fractured field. In New Hampshire, for instance, so-called establishment support was divided among Kasich, Bush, Rubio and New Jersey Gov. Chris Christie.

That's no longer the case.

So the big question for the Republican front-runner on Tuesday night is whether he's somewhere near his ceiling or whether he has room to grow.

If Trump's numbers keep climbing and neither Rubio nor Cruz can stay close, he could be a runaway train bound for the Republican National Convention in Cleveland.

Rubio's rise

The nights of Rubio selling third place as a win are over.

Since Jeb Bush dropped out of the Republican race Saturday night, Rubio has quickly worked to lock down the party's establishment -- picking up former Bush donors and releasing a cascade of endorsements from governors, senators and congressmen Monday.

Though Ohio Gov. John Kasich remains in the race, Rubio appears close to locking down the party's more moderate and establishment types. It's a testament to his own political talent, but also a recognition that if the GOP is to stop Trump from winning its nomination, it's now or never.

Now, Rubio has to get voters to buy in.

The Nevada caucuses are the first test of whether Rubio can consolidate the anti-Trump forces within the GOP and become the party's clear alternative.

Timing is crucial: He needs momentum headed into the Super Tuesday swath of twelve states voting on March 1 -- and especially before March 15, when Republican contests become winner-take-all.

Can Cruz come back?

The toll of the persistent attacks from Trump and Rubio -- Cruz is a liar -- became clear Monday when the Texas senator canned Rick Tyler , his campaign's communications director.

Far from clearing up his problems, that move might have only served to underscore the complaints that Cruz's opponents have repeatedly lodged about his campaign tactics and attack ads.

After a third-place finish in South Carolina, and under intense scrutiny, Cruz is now in jeopardy of become the odd man out of the GOP race.

The establishment is rallying around Rubio. Trump has proven he can win over Evangelicals and rock-ribbed conservatives who make up Cruz's base. So who can Cruz win?

His third place finish in South Carolina was a stinging setback for a candidate who is betting his campaign on a strong showing in the South on Super Tuesday. A stronger than expected showing in Nevada could go a long way toward easing the weaknesses that were exposed in South Carolina.