Wherever the president decides to campaign, Republican criticism will follow. For national Republicans, a visit by the president or Vice President Joe Biden offers an opportunity to tie a Democratic candidate to a president with falling approval ratings — just as it was for Democrats with President George W. Bush during the 2006 cycle.

According to pollster Hart, that is the major benefit of a surrogate like Clinton — the current administration’s policy problems cast a smaller shadow on the candidate.

“Clinton can take a Democratic message directly to voters without any static,” Hart said.

“He is a safer surrogate,” Democratic pollster John Anzalone said of Clinton. “But I don’t think surrogates win elections. At the end of the day, you need to win on your own.”