Mike Pence, Donald Trump's Republican running mate for the U.S. presidency, narrowly won last night's debate against Hillary Clinton's VP candidate, Tim Kaine, according to a poll of voters who watched the vice-presidential bout.

But Pence's performance appears unlikely to have a significant impact on Trump's chances of taking the White House.

The CNN/ORC poll, surveying 472 registered voters who had previously been contacted and said they would watch the debate, found that 48 per cent of respondents felt Pence had done the best job, compared with 42 per cent for Kaine.

But that six-point edge pales in comparison to the 35-point margin that Hillary Clinton had over Donald Trump in CNN's poll conducted just after the first presidential debate on Sept. 26.

The small scale of Pence's win is similar to Paul Ryan's four-point edge over Joe Biden in 2012's vice-presidential debate — a debate victory that did not translate into an election victory for Ryan's running mate. On the other hand, the wide margins of victory recorded in CNN's polling for the 1992, 1996 and 2008 vice-presidential debates were put up by winning tickets (Al Gore in 1992 and 1996 and Biden in 2008).

Part of the problem for Kaine may have been that he did not live up to expectations. The poll found that 43 per cent of watchers felt he had done worse than expected, while just 38 per cent thought he had done better. Those are worse numbers for Kaine than put up by Biden, Ryan or Sarah Palin.

Pence, on the other hand, surpassed expectations. Fully two-thirds of voters felt he did better than expected. Only 14 per cent thought he had done worse. In a losing campaign in 2008, however, Palin had beaten her expectations by an even bigger margin than Pence did.

Boost for Trump campaign?

If Pence's performance, then, is similar to those put up by Ryan in 2012 and Palin in 2008, that does not bode well for his chances on Nov. 8. Nevertheless, the poll does suggest that Pence did do his ticket some favours.

While just over half of respondents said the debate would have no effect on their vote, 29 per cent did say it made them more likely to vote for Trump, compared with 18 per cent who said it increased their likelihood of voting for Clinton.

Most of those saying they were more enthusiastic for the Trump/Pence ticket, however, were Republicans or people who were already planning to vote for Trump. 

But by a margin of two-to-one, self-identified Independents said the debate made them more likely to vote for Trump over Clinton.

From unknowns to knowns

Before the debate, much was made of the lack of profile of these two vice-presidential candidates. One poll had shown that more than 40 per cent of Americans couldn't name the two VP nominees. But the CNN poll suggests that Kaine did more harm to his profile than Pence did.

The debate increased Kaine's favourability rating by only one point, but boosted his unfavourability by 12. Pence, on the other hand, saw his unfavourables jump by just four points and his favourables increase by seven.

Still, neither candidate gained much of an advantage out of these shifts. Their ratings are now nearly identical. The poll found that 56 per cent of debate-viewers now have a favourable view of Kaine. For Pence, that number is 57 per cent. Both candidates scored a 40 per cent unfavourable rating.

The poll also showed that Tim Kaine was seen as the candidate who "spent more time attacking his opponent", "did the better job defending his running mate", and "had a better understanding of the issues." Two of those three are positive indicators for Kaine.

Pence, however, scored better on being "more likeable." That could be an even more positive result for Pence as the election approaches — perhaps he will play a larger role in Trump's campaign. But Paul Ryan and Sarah Palin, two candidates who did not become vice-presidents, were also seen as the more likeable debaters in 2008 and 2012. 

In the end, it will be the top of the ticket that will decide this election. Pence may have given his campaign a small bit of good news this week. But it will be Donald Trump and the next two presidential debates that will determine whether or not Mike Pence will become vice-president.