CNN Poll of Polls: Biden holds a nine-point lead over Trump ahead of the party conventions

Biden, who is set to accept the Democratic nomination later this week, is backed by 51% of registered voters nationwide, while 42% support Trump.

The Poll of Polls includes the six most recent national telephone polls measuring the views of registered voters. Only two of the six included polls were conducted entirely after Biden announced California Sen. Kamala Harris as his running mate.

The polls conducted after Biden's historic selection of Harris as his running mate largely find the pick to be received positively by the public: 52% of registered voters in CNN's poll called it an excellent or pretty good pick, including 82% of Democrats.

In the Washington Post/ABC News poll, 54% of Americans said they approved of Biden's choice of Harris, with 86% of Democrats approving of the pick.

But as voters voice their approval of Harris, they are also signaling their disapproval with Trump in recent polls that show his approval rating is largely underwater as the party conventions begin.

In the CNN poll, 42% of Americans approve and 54% disapprove of the President. In the Washington Post/ABC News poll, his rating stands at 43% approve to 55% disapprove. The NBC News/Wall Street Journal poll finds 44% of registered voters approving of the President, with 53% disapproving, while the Fox News poll shows Trump's rating among registered voters at 44% approve to 54% disapprove.

Several recent polls have pegged interest and enthusiasm about the presidential race at historic levels. CNN's polling found -- for the first time in CNN's trend on this question back to 2003 -- a majority of voters saying they were "extremely enthusiastic" about voting in the presidential election. The NBC News/Wall Street Journal poll found 79% rating their interest in the election as a 9 or 10 on a 10-point scale, higher than in previous cycles.

The Fox News poll found interest in the election at a new high: 62% of voters said they were "extremely interested" in the presidential election, up from 54% in June and higher than it's been in polling back to the 2012 cycle.

The CNN Poll of Polls is an average of the six most recent non-partisan, live operator, national telephone surveys on the general election matchup between Biden and Trump among registered voters. The Poll of Polls includes results from the Washington Post-ABC News poll conducted August 12-15, the CNN poll conducted by SSRS August 12-15, the NBC News/Wall Street Journal poll conducted August 9-12, the Fox News poll conducted August 9-12, the Monmouth University poll conducted August 6-10 and the NPR/PBS NewsHour/Marist poll conducted August 3-11. The Poll of Polls does not have a margin of sampling error.