Among seven potential Democratic presidential contenders, Hillary Clinton is the overwhelming favorite — and the third-most liberal candidate. How the other candidates are arrayed on an ideological spectrum could make her run for the White House easier than the last time out.

In some ways, the cast of candidates for 2016 resembles the group from the 2008 race, with a field of stalwartly liberal politicians. Mrs. Clinton was slightly more liberal in 2008 than now, according to Crowdpac, which scores politicians on a left-right scale of -10 to 10. (Crowdpac bases this mainly on campaign contributions, but also on votes and speeches.) Her problem was that Barack Obama, who was further to the left of her — at -7.8 to her -6.9 — also had the donors who were to the left of her. He ran a better campaign, particularly in Iowa, and benefited from a surge in money from small-dollar donors.

This time, Senator Elizabeth Warren of Massachusetts (-8.2) and Bernie Sanders (-8.3), Vermont’s independent senator, are to her left. Ms. Warren has the higher fund-raising profile of the two, with a leadership PAC that raised more than $2 million during the 2014 election cycle. But she and Mrs. Clinton (and to a lesser extent Mr. Sanders) would be competing for a similar pool of donors. During her 2012 Senate race, Ms. Warren raised more than $3.4 million from individuals who also gave to Mrs. Clinton's presidential campaign, Federal Election Commission data shows.