Former secretary of state Hillary Clinton's anticipated campaign launch Sunday will mark the culmination of years of speculation about her presidential ambitions. But her official declaration is only the beginning of a long campaign -- and there are still burning questions over how (and if) her team will incorporate the lessons from her failed 2008 run. There have been advance clues to some of the mysteries still surrounding her presidential bid, heading into its Sunday debut -- but here are a few that are still not-quite-resolved:

What is Clinton's core message, and how will she deliver it?

Clinton famously struggled to communicate her vision to voters during the 2008 election --  in part because dysfunction within her campaign team hindered her efforts, but also because the candidate herself frequently seemed overly scripted and guarded. (That was, of course, made all the more clear by then-Sen. Barack Obama’s considerable talents for retail campaigning.)

Those are errors she’s not eager to repeat.

We've already gotten a sense of how she might approach the race: As the Post’s Anne Gearan and Dan Balz reported earlier this month, Clinton will focus on an economic message aimed at the middle class, and avoid big rallies in favor of small events in the hopes of connecting with voters more authentically:

“The approach — described by Democratic strategists and advisers familiar with her plans — is intended to address some of the key shortcomings of Clinton’s 2008 run for the White House ... The go-slow, go-small strategy, these advisers say, plays to her strengths, allowing her to meet voters in intimate settings where her humor, humility and policy expertise can show through.”

Related: What is her rationale for running?

Another big problem for Clinton in 2008 was the overwhelming sense that she was the inevitable candidate, which led many to accuse her of failing to develop an actual rationale for a Hillary Clinton presidency -- to tell voters why she should be president, and lay out in detail what she'd do once she got to the Oval Office.

That failure continues to loom over her 2016 bid for the White House. As Democratic strategist David Axelrod noted late last year, "I think the danger for Secretary Clinton is that, as was the case in 2007, her candidacy is out in front of the rationale for it."  That rationale may very well rest on her experience as the nation's chief diplomat under President Obama -- and her memoir "Hard Choices" strongly indicates that will be the case

How will she talk about President Obama?

President Obama remains a deeply divisive figure in American politics, a reality Clinton will have to grapple with as she seeks to differentiate herself from her would-be Democratic predecessor without alienating him or his allies. Beyond that, Obama fatigue” will almost certainly pose a problem for Clinton because of her central role in the president’s cabinet during her tenure as secretary of state.

What role will former President Bill Clinton play?

Former President Bill Clinton could be a hugely influential surrogate for his wife’s presidential campaign -- but he could just as quickly become a major distraction, as evidenced by his tumultuous role during her 2008 run. On several occasions missteps by the former president distracted from Clinton’s message and resulted in the campaign losing control of the narrative.

The Post's Chris Cillizza noted last month, it remains to be seen how effective the former president can be this time around: "[H]ow her husband will be used on the campaign trail -- particularly after the disastrous results of his forays into the 2008 campaign -- is a critically important question for her campaign-in-waiting. Views on what the best role is for Bill Clinton are divided within Democratic circles."

Will the State Department email scandal -- or Clinton Foundation foreign funding questions -- leave a mark?

The controversy over Clinton's use of a private e-mail address has faded a bit -- but is the issue really gone for good?

Republicans have a series of Hill inquiries in the works, in a bid to keep the issue alive headed into 2016. And, as Anne Gearan and Phil Rucker reported Friday:

"Within hours of news reports Friday morning that Clinton would launch her campaign this weekend, the Republican National Committee announced an online ad as part of its "#StopHillary" campaign to highlight scandals over her use of private e-mail at the State Department and foreign donations to her family's charitable foundation."

That said, Clinton may be in a better position to deflect those criticisms now that she's formally launched her campaign -- with a press shop in place and, presumably, a rapid response team equipped to...well, respond.