In the modern era, the number of candidates who have won the nomination of either major party without winning either Iowa or New Hampshire remains zero. Every election year, some candidate tries to make the case that he has a strategy for victory that doesn't include winning either of these states, and every election year, another candidate goes home a loser. In 2008, it was Rudy Giuliani. In 2012, it was Newt Gingrich.

This year, as much as candidates like Marco Rubio have tried to make the case that there is a plausible victory scenario that doesn't involve winning either of the first two contests in this year's primary, all the Republican candidates know that realistically, they have less than a month left to make their final case to voters (and donors) before it's time to pack it up and quietly head for home (or stick around for the pure pleasure of playing spoiler like Mike Huckabee did in 2008).

Up until this point, the Republican debates have been largely collegial, in spite of the presence of Trump on stage. Although Trump has been at the center of a number of sharp-elbowed exchanges, the other candidates have been largely polite with each other, even when disagreeing. And of course, the main battle everyone has been waiting to see between Cruz and Trump has repeatedly failed to materialize. So while the debates have been perhaps more entertaining than they have in years past, they have also been largely nice. Here are five reasons that is likely to end tonight.

1. The gloves have come off between Cruz and Trump. Although Cruz and Trump flirted with open conflict before the last debate, the sparks were called off when Cruz refused to engage Trump's bluster, which Trump took as a sign of respect. However, Cruz's challenge to Trump, which is the first genuine one he has faced this campaign season, has forced Cruz to respond with a series of escalating attacks on Trump, basically accusing him of being a Hillary plant on Tuesday and then calling him a liberal New Yorker yesterday. This time, at long last, Cruz shows no signs of going back into "friendly" mode and voters will likely get to see some testy exchanges between the two, especially since the "birther" issue seems to have rankled Cruz in ways no other candidate's attacks have prior to this point.

2. Less candidates on stage. For this debate, the field has been winnowed to a more manageable 7 total candidates, which means each candidate will (theoretically) get more time on camera. This means that there will be more opportunity for the lengthy sort of back and forth that generates the sort of on-screen acrimony that leads to memorable nasty debate moments. There's ample evidence that several of the candidates in this field don't like each other personally, and even though one of the prime instigators (Rand Paul) will be absent, one other major irritant remains. Which brings us to..

3. Chris Christie DGAF. Christie has decided to unleash the last trick left in his arsenal, which is to treat each and every one of his Republican opponents like they were a semi-literate YouTube commenter who was criticizing his latest performance in a townhall meeting. In the last two weeks, Christie has gone relentlessly negative against Rubio and Bush in particular, hoping to seize on some momentum for a surprise New Hampshire finish. Christie will not let anything silly like debate rules or a moderator get in his way if he feels like something needs to be said about one of the other candidates on stage, and if past history is any indicator, his attacks will likely be a) colorful, b) intensely personal, and c) largely bovine fecal material, from a factual standpoint. Expect multiple dustups between Christie and other candidates on stage tonight.

4. FoxBusiness knows what they are doing. Several of the other networks who have hosted debates during this campaign season have tried to cause fights between the candidates, but they have largely failed because they don't really understand what makes conservatives or Republicans tick. FoxBusiness demonstrated in the last debate that they do not suffer from this affliction, as they ran what was widely considered the best debate of the campaign season so far in their prior effort. Expect this debate to succeed where others have failed, in terms of effectively highlighting the differences both in policy and temperament between the candidates. The end result of this talent will likely be to draw out the increasing desperation and pressure that all the candidates (including Trump) are feeling.

5. Jeb Bush needs to show something to his donors. As the Jeb Bush campaign has fallen further and further in the polls, his operation has resorted to increasingly desperate attacks against the other candidates in the field. While you weren't looking, Bush has gotten much better and less awkward in recent weeks when it comes to delivering attack lines. It will probably be too little, too late for his campaign, but expect Bush to be in the middle of at least one entertaining dust-up tonight that may allow him to play spoiler for someone else in the field.

At the end of the day, if you enjoy bare-knuckled political brawls, tonight's debate promises to be a treat. Grab your popcorn and get ready to enjoy it.