Watch Live:
American Flags on Brooklyn Bridge Replaced With White Flags
Biggest Impediment for Hillary Clinton: Her Former Boss
PHOTO: Former Secretary of State Hillary Rodham Clinton waves as she arrives to receive the Liberty Medal during a ceremony at the National Constitution Center, Tuesday, Sept. 10, 2013, in Philadelphia.

Will President Obama again block Hillary Clinton from becoming president?

In 2008, the odds of a Democrat winning the White House were very good. The political environment in the aftermath of eight years of President George W. Bush was set for a change to an opposing political party. President Bush's approval ratings were way down, many in the country were tired of the way he ran Washington, D.C., and they were frustrated by his apparent inability to bring the country together.

Any Democrat who got the nomination that year had a high likelihood of winning the general election. As I have said before, the most dominant factor in presidential elections is the existing environment parties and candidates face.

In that year, then-Sen. Obama became the Democratic standard bearer, having beaten Hillary Clinton in a close primary contest. He then went on to win a fairly easy victory over John McCain in the general election, as the Arizona senator struggled to distance himself from all the baggage that came from President Bush's second term.

It wasn't the tactics, or the media, or the campaign staffs that determined victory -- by and large, it was where the country wanted to go.

Today, Obama is nearly in the exact same position as Bush was at this same point. His approval numbers are down, the country has lost faith and trust in his leadership, and voters hunger for someone who can make Washington work again.

The political environment at the moment (and we have two years to go until 2016, so things could change) is tilted in favor of a Republican winning the White House no matter who the Democratic nominee will be.

Hillary Clinton looks to be on the verge of running in a Democratic nomination race with virtually no real opposition. She will be extremely difficult to beat. She starts out nearly 60 points ahead, and all other strong challengers are seemingly ceding her the nomination.

But she faces a very difficult general election environment if the Republicans nominate any reasonable candidate. This difficult general election environment created in no small part by Obama's two terms in office.

Obama, having beaten Hillary the first time in 2008, may actually cause her to lose if she is the nominee in 2016 because independent voters have a strong desire to change from the current incumbent's leadership.

And interestingly we have seen this kind of scenario unfold recently before. Bush dispatched McCain in the primaries in 2000, and then when McCain was able to secure the Republican nomination in 2008, he faced a general election situation in which it was nearly impossible for him to win, due to independent voters wanting change from the incumbent party's leadership.

Bush roadblocked McCain two separate times for the presidency, once in the primary and then indirectly in the general election. And now Obama is set to repeat this history as regards Hillary Clinton and her quest for the president, roadblocking her one more time in the 2016 general election.

Much can change in the months ahead. The Republicans recently have been known to shoot themselves in the foot, and Clinton may even decide not to run at all, but the biggest impediment she is likely to face to capturing the White House is once again her now friend but nemesis from 2008, Barack H. Obama.

Whether this ironic situation turns out to be a comedy or tragedy for Clinton and the man she worked for as secretary of state, we will know in the unfolding of time, but as the saying goes, sometimes your friends can be your own worst enemies. The good news for her is she could turn to her former colleague Senator McCain for advice on how to process this storyline.

There you have it.

Matthew Dowd is an ABC News analyst and special correspondent.

Opinions expressed in this column do not reflect the views of ABC News.

More ABC News