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Former U.S. President Bill Clinton speaks during the Clinton Global Initiative's annual meeting in New York, Sept. 29, 2015. Reuters

Welcome back to the campaign trail, former President Bill Clinton. After months of internal advising and a recent uptick in fundraising appearances, he is now expected to take to the campaign trail in Iowa this weekend on behalf of his wife, Democratic presidential candidate Hillary Clinton.

It will be the first time the former president makes a public appearance on behalf of his wife's campaign after some political observers expected that he wouldn't start doing so until much later in the race.

The decision to bring Bill Clinton on the campaign trail is significant. Hillary Clinton and her campaign have made repeated attempts to distance her image from that of her husband and of the Obama administration, for which she served as U.S. secretary of state from 2009 to 2013.

"I am not running for my husband's third term or President Obama's third term," Hillary Clinton likes to say on the campaign trail. "I'm running for my first term."

The participation of Bill Clinton comes amid rising polling numbers for Hillary Clinton's chief opponent in the 2016 race, U.S. Sen. Bernie Sanders. In national averages of polls, Clinton leads by 20.7 points, according to Real Clear Politics. She trails Sanders in New Hampshire by 5.7 points, however. New Hampshire is an early-nominating state and could provide momentum for the Vermont senator should he win that primary.

But it's not as though Bill Clinton has been completely absent from the campaign. Staying mostly out of the public light, he headlined big fundraisers for his wife in September and supported her publicly on cable television when Republican front-runner Donald Trump took swipes at her tenure as secretary of state.

Bill Clinton is a particularly popular figure in American politics. In a recent NBC/Wall Street Journal poll of adults, 56 percent indicated a positive impression of the former president. Just 26 percent expressed a negative perspective toward him.

Still, there is some liability. The Hillary Clinton campaign took some heat in 2008 when Bill Clinton referred to then-Sen. Barack Obama's anti-war position as a fairy tale while on the Rev. Al Sharpton's nationally syndicated radio program. The African-American community criticized his remarks as having been intended to say that Obama's overall message and drive to be the first black president were fairytales.

Four years later, however, Bill Clinton was on the campaign trail to ensure that Obama won a second term as president. During that time he received the nickname "explainer-in-chief" for a Democratic convention speech in which he eloquently defended Obama's first term.