The Republican field enters the second debate with some unexpected changes in the last month: Donald Trump's national poll numbers have surged ahead of Joe Biden while Ron DeSantis has continued to fade, and Nikki Haley has emerged as the non-Trump candidate with the most momentum.

The big questions for the second debate are: will the field shrink fast enough to have a chance to catch Trump? Do any of the candidates have a real plan for renewing America and its economy or are they going to just attack each other? Can DeSantis revive his campaign? Will Haley have another win and sustain her momentum?

The breakouts of the first debate were Vivek Ramaswamy and Haley. But Ramaswamy looks more and more like a one debate wonder as he is sinking quickly in early primary states. In contrast, Haley has been consistently coming up in the key primary states as she has moved to third in Iowa and second in New Hampshire. She has emerged as the real winner of the first debate and while her numbers are still small, they are growing quickly. In addition, in national head-to-heads she is beating Biden by the same margin as Trump, giving her a strong electability argument. Tim Scott remains well liked by Republican voters but did not gain any traction out of the first debate. 

What many pundits miss is that the Republican party – and its primary electorate – is mostly a suburban party. The GOP does very well in rural areas, but not a lot of the country lives in those. Just over half of Republican primary voters are suburban and just under half are women according to a recent Wall Street Journal poll. Haley is winning over these voters and has an opportunity to grow, especially as she differentiated herself at the first debate with a more pragmatic position on abortion. While she is personally strongly pro-life, she acknowledged the limits of divided government and did not over-sell sweeping abortion bans like the other candidates and this set her apart. 

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Independents can vote in the GOP primaries of 23 states, and they are starting to move towards Haley. In this month’s Harvard CAPS/Harris Poll, Haley beats Biden by 4 points in a head-to-head for the first time with 40 percent of the Independent vote. Scott also beats Biden by 2 points in the poll. 

A strong economic plan could be the biggest differentiator in debate number two. Inflation and the economy remain the top concern for voters, but the candidates barely spoke about economic issues in the last debate. Scott’s new balanced budget plan is a step in the right direction though few voters have heard about it yet. Inflation, the economy generally, immigration and crime are top Republican and national issues and yet most of the debate from these candidates has been about cultural issues like parental rights. Arguably DeSantis squandered his lead getting involved in cultural dust-ups that got him national publicity but at the expense of his reputation as a leader. His 6-week abortion bill hurt his electability argument and branded him as too conservative. He went from the candidate that Democrats feared to one that they believe can be beaten. 

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Chris Christie is showing some signs of life as third in New Hampshire, but he is on that stage to attack Trump and without Trump in the debate he is mostly shadowboxing. Mike Pence is the first vice president in modern times to run against the president he served and that seemingly limits his ability to grow as some see him as too Trump and others as not Trump enough.

The newest ABC News/Washington Post poll gives Trump a massive 10-point lead over Biden with registered voters. The poll may be an outlier, but it hurts the non-Trump field whose campaigns are based on how they are the ones who can defeat Biden. It upsets the conventional wisdom that Trump can’t win and if there are more polls like this, more Republican voters may just stick with Trump. 

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No doubt the candidate research teams are busy coming up with new attack lines against their opponents and Democrats are hoping for the Republicans to attack each other so ferociously that no one wins the debate and the Republican field fails to consolidate. Primary electorates are famously volatile, so the GOP primary is far from over and there are signs that Haley could be the surprise of the cycle if she can keep her momentum coming out of this debate.

Mark Penn is Chairman and CEO of MDC Partners and managing director of the Stagwell Group. He was chief strategist on Bill Clinton’s 1996 presidential campaign, Hillary Clinton’s 2000 Senate campaign, and Mrs. Clinton’s 2008 presidential campaign. Follow him on Twitter @mark_penn.