'Win' does not mean 'Who scored more political points?' Not 'Who had the best one-liners?' Not 'Who got more talk on the news shows?' Not even 'Who looked more presidential?' To political strategists, 'win' means something very specific: Who gained the most votes? The purpose of the debates, from a political strategy point of view, is to gain votes, particularly among undecided voters. Polls later this week will tell the REAL answer to that question, and 'Who won the debate?' will be answered by 'How many undecided voters decided for Hillary or for Trump?'

There are two key groups of undecided voters at this stage of a political campaign: (1) Those who are split between the two major-party choices; and (2) Those who are undecided about whether they care enough to get out and vote. The polls actually measure only group (1), by simply asking voters whether they are undecided. For group (2), the pollsters estimate voting turnout based on historical averages, and factor those expected turnout rates into their predictions – that's much more art than science, and is the reason polls differ from one another in their conclusions.

For Trump, group (2) mostly comprises suburban white middle-class voters – who traditionally have a high voting rate. For Hillary, group (2) mostly comprises young people and minorities – who traditionally have a low voting rate. Trump's goal in the debates is to inspire suburban white middle-class voters enough that they stick with him instead of Hillary, and that they stick with him enough to get out and vote. Hillary's goal in the debates is to inspire young people and minorities enough that they register to vote and then go vote on Election Day. Minority voters appear to be fully in Hillary's camp already, so Hillary's goal has become inspiring young voters – with a high overlap to Bernie Sanders supporters.

Barack Obama won the presidency by a wider margin than the polls predicted because he inspired young people and minorities to register to vote, and then to vote. The pollsters underestimated those voting rates, because those groups have an awful voting history – in particular, young people vote at rates under 40% (meaning fewer than half of voters aged 18-29 actually bother to get through the process of registration and voting). Compare that to voting rates of around 80% for suburban white middle-class voters – that means that if a pollster happens to call a young person, their answers are counted at only 1/2 of the value of an answer from a suburban white middle-class voter. That skews the poll results if the pollster's estimates are wrong – which is why Obama beat Mitt Romney in 2012 by 3% when the polls predicted a Romney victory by 1%. Bernie Sanders similarly did better than the the polls in several primaries – and the big question now is whether Hillary can do the same with those same young voters.

Let's look at the numbers for the first debate. About 81 to 84 million people watched; about 20% of those are undecided voters, or about 16 million undecided voters. Since all of them will make up their mind by election day, and there are four debates scheduled, each debate might be considered responsible for helping 5% of the undecided voters make their decision – that's 4 million votes to be split by the 'winner' and 'loser' of each debate.

Trump entered this debate a little bit behind in the polls -- his goal was to get enough of those 4 million undecided voters to catch up. His tactic was to demonstrate his business success (which he touted repeatedly, on every topic from frugality on his own income taxes to pointing out the weaknesses of several negotiated deals with foreign countries), and to exemplify "thinking on his feet," speaking extemporaneously rather than using "canned responses" prepared in advance. Certainly Trump followed through on those two tactics, which focus on characteristics important to his base. The weekend polls in a few days will determine if Trump succeeded in converting the undecided white middle-class suburban voters who were his target audience – in which case he was right that he 'won.'

Hillary's goal was to target sub-groups of the undecided voters: specifically, young voters, white suburban middle-class women, and minorities. She targeted each of those groups separately, at different times during the debate. For the young voters, Hillary talked a lot about the failures of "trickle-down economics," a populist message that resonates with progressives who supported Bernie Sanders and idolize Elizabeth Warren. For the women voters, Hillary focused on Trump's sexism in calling out a beauty queen who became overweight; Alicia Machado quickly became the favored topic on all of the political pundit shows. For African-American voters, Hillary discussed the "systemic racism in our criminal justice system," using a term that Bernie Sanders favored in the primaries. For Latino voters, Hillary will presumably focus on them more in the next debate when immigration is a central topic, but Alicia Machado served as a symbol for anti-Latino racism as well as sexism. To my pundit ears, all of those topics seemed pre-planned to target specific audiences of undecided voters – look for polls breaking down those demographics to see if Hillary succeded.