Story highlights According to a CNN poll of polls, Donald Trump tops the GOP field with 31%, well ahead of Marco Rubio's 15%

In that same analysis, Bernie Sanders' 54% to 40% advantage over Hillary Clinton is down slightly

(CNN) On the eve of New Hampshire's presidential primaries, a new CNN Poll of Polls finds both Donald Trump and Bernie Sanders are holding on to substantial leads in their respective races, but each faces an opponent whose support is on the rise.

Sanders' 54% to 40% advantage over Hillary Clinton is down slightly from a 55% to 37% lead in the previous Poll of Polls. No public polling has found Clinton in the lead in New Hampshire since November.

Trump tops the GOP field with 31%, well ahead of Marco Rubio's 15%. Rubio has picked up four points since the previous New Hampshire Poll of Polls, the biggest change in the averages in the last week. Ted Cruz follows with 13%, John Kasich at 11% and Jeb Bush at 10%. This pack of four -- Rubio, Cruz, Kasich and Bush -- has been jockeying for second place in the state for some time. The fifth candidate often included in the group, Chris Christie, has generally seen his support dwindle, and now stands well behind, dropping two points in this week's Poll of Polls to an average of 5%. Carly Fiorina ties Christie at 5% and Ben Carson rounds out the group with 3%.

But the overall wide margins aren't an indicator that the political world can turn its attentions away from the Granite State just yet. All of the polls included in the Poll of Polls were completed prior to Saturday night's Republican debate, however, and it remains to be seen how that will impact voters in the final days of the campaign.

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