Democratic Senate challenger Alison Lundergan Grimes left, speaks with former President Bill Clinton as they are introduced at a fundraiser at the Galt House Hotel, Feb. 25, 2014, in Louisville, Ky.

All eyes will yet again be on Hillary Clinton today as she makes her first campaign appearance of 2014 with a fundraising event for Pennsylvania congressional candidate, and Chelsea Clinton's mother-in-law, Marjorie Margolies.

Clinton, who has largely shied away from political events in the past year, is making an exception for her in-law, who could use a boost in the polls. And f or Margolies, who has also had the public support of former president Bill Clinton, it's a pretty nice deal.

No two political figures have as much endorsement power as the ones who bear the Clinton name. Last month a poll showed Bill Clinton's favorability to be on par with Pope Francis, and this month at a health care conference Hillary Clinton was likened to a "rock star."

Their influence and star appeal makes them the most sought-after campaign surrogates in the 2014 midterm races. Just as book publishers want Oprah and designers want Anna Wintour, Democratic candidates want the Clintons.

But how does one get a political push from the power couple? Is raw talent and political charisma enough for a candidate to get on their radar, or does touting a Clinton by ones side require a little something more?

Here's a list of reasons that may compel one, or both, of the Clintons to go out and stump:

A family tie appears to go a long way for the Clintons. While Bill Clinton has been a fairly active campaign surrogate, Hillary Clinton has yet to make a single appearance or endorsement on behalf of anyone this midterm cycle - with the exception, only now, for the woman she's about to share a grandchild with: Marjorie Margolies. This afternoon in New York City, Hillary Clinton will be the special guest at a fundraising event on behalf of her in-law, a former Pennsylvania congresswoman who lost reelection in 1994 and is now hoping to get her seat back. Bill Clinton has been even more involved with the campaign, especially as she looks for a boost in the home-run stretch. Last month he headlined a fundraiser for Margolies in Philadelphia and on Wednesday, less than one week before the state's primary, he touted her accomplishments in a new campaign spot, a move Roll Call described as "potentially game-changing." This isn't the only time a Clinton has backed one of their own. Ten years ago, Hillary Clinton stumped for her brother, Hugh Rodham, in Florida when he ran for a U.S. Senate seat.

It doesn't so much matter if it's a high-profile or a low-profile race, a candidate that's a long time friend of the Clintons (or once upon a time did them a friendly favor) could likely find themselves with a Clinton standing beside them. Bill Clinton has brought his star power this midterm to stump for his good friends' daughter, Kentucky Senate candidate Alison Lundergan Grimes. Last year, Hillary Clinton made a rare campaign appearance for her personal and political friend, Virginia Gov. Terry McAuliffe, who has raised millions for the Clintons' causes over the years and once loaned them money to purchase a home. And Marjorie Margolies could fall under this grouping too. Back before they were in-laws, then-Rep. Margolies cast a tie-breaking vote in congress that saved President Clinton's 1993 budget, but essentially lost Margolies her congressional seat. Perhaps the Clintons now feel they owe her a favor.

Hillary Rodham Clinton and campaign chairman Terry McAuliffe celebrate at her primary election night celebration at the Charleston Civic Center in Charleston, West Virginia on May 13, 2008

The big picture can often be a factor. When there's a high-stakes, competitive race, that's when calling in a Clinton can be critical. Take the Kentucky Senate race, for instance: Grimes is currently in a dead heat against Republican Senate minority leader Mitch McConnell. But Democrats are hopeful that the Clinton name could be what it takes to grab the coveted spot. Bill Clinton, aptly called Campaigner-in-Chief, also gets sent out for damage-control. Last month he stumped on behalf of Arkansas Sen. Mark Pryor, who is considered by the Democratic Party to be an endangered incumbent candidate in 2014.

Bill and Hillary Clinton are loyal to the people who worked for them. Bill Clinton has often thrown his political support behind his former staffers that later seek office, including Chicago Mayor Rahm Emanuel and Steve Grossman, the DNC chair while Clinton was in the White House who later campaigned for Massachusetts treasurer. This year, Bill Clinton has stumped for Arkansas congressional candidate James Lee Witt, who was his FEMA director for both terms during his presidency. And both of the Clintons gave big endorsements to New York Mayor Bill de Blasio during his mayoral campaign last year. De Blasio served in Bill Clinton's administration in 1997, and later became Hillary Clinton's campaign manager during her 2000 New York Senate race.

De Blasio is sworn in as NYC's 109th mayor by President Bill Clinton on the steps of City Hall on January 1, 2014 in New York City.

The uncertainty of 2016 hovers above everything Bill and Hillary Clinton do these days. And if the Clintons are in fact thinking long-term (i.e. potentially embarking on Hillary Clinton's presidential race), thinking about who they've endorsed now isn't as revealing as who they may choose to endorse in the near future. Strategically, the Clintons could decide to back candidates in 2014 that could be politically advantageous to them in 2016. If this is the case, candidates from politically important states, such as Sen. Jeanne Shaeen in New Hampshire or other candidates in Iowa and Florida, could suddenly find they've scored one of those coveted visits from a Clinton.

ABC's Rick Klein and Michael Falcone contributed to this report.