The major issue in this final debate on domestic policy was taxes. McCain's idea: “If nobody likes taxes, let's not raise anybody's taxes, OK”. Here's the problem: governments need money regardless of whether the economy is healthy or not. So, under McCain's proposal, if no one's taxes were raised, the rich would stay rich and the poor would stay poor. So this is not an effective solution.
Obama's response: “Nobody likes taxes, but ultimately, we've got to (i.e. the government has to) pay for core investments” which are necessary to sustain the economy. Obama clearly won this debate because his argument is that 95% of people, most of whom are middle-class income earners who live off of their salaries, will get a tax cut. On top of this, it doesn't make sense to increase taxes on lower-income people because if you do that, how will they eat and sustain their lives?
In addition, Obama slammed McCain for wanting to cut out critical programs: “I do want to just point out that autism or other special needs will require additional funding if we're going to get serious in terms of research…And if we have an across-the-board spending freeze, we're not going to be able to do that”. Here, Obama is cri0ticizing McCain for wanting to cut things that should not be cut and (undoubtedly) keep programs that should be cut.
According to CBSNews.com senior political editor Vaughn Ververs, “John McCain turned in an energetic, focused and at times, emotional performance. But he needed something more in order to change the underlying dynamics of this race (and he didn't do that). Obama was solid, on message and mostly mistake-free, likely stunting any major gains for the Republican. McCain may have righted the ship to some extent, but time is running out for him to make up ground”.
The final result: Obama won by a margin of 53-22 among surveyed respondents.