Although Joe Biden and Bernie Sanders are still at the top of all the polls, the fight for the Democratic nomination is already down to Elizabeth Warren vs. Kamala Harris.

The reality is that Biden and Sanders continue to slide in the polls from their once lofty perches as Warren and Harris continue to climb.

The erosion of Biden and Sanders’ poll numbers is rarely reversed. The gains by Warren and Harris in the polls can continue -- and likely will do so. And while Biden and Sanders will have the money to stay in the race through Super Tuesday, it will be Warren and Harris who will do battle to win the nomination which could be decided by Super Tuesday.

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The latest Fox News poll makes it clear the fate of these four candidates are intertwined. Sanders has dropped eight points since March to his low of 15 percent while Warren has picked up eight points to her high of 12 percent during the same time.

Meanwhile, Biden has dropped two points since May while Harris has increased two points since the June debate to her high of a ten percent approval rating.

That’s why Warren and Harris have the chance in the debates this week to put Sanders and Biden away. Much of the gains Warren has made in the polls has naturally come at Sanders’ expense.

Despite his current lead in the polls, if Biden has another bad debate Wednesday night then the bottom will fall out and voters will start to abandon him.

Harris’ performance at the last debate when she took on Biden not only catapulted her to the top tier but also revealed that the former vice president is a fragile front runner.

Despite his current lead in the polls, if Biden has another bad debate Wednesday night then the bottom will fall out and voters will start to abandon him.

A bad debate performance could come from a self-inflicted wound by the candidate, a knockout punch by Harris, or an assist from Corey Booker, who has telegraphed that he will go after him. But, make no mistake if Biden falters then it is Harris who will benefit -- no matter who is responsible for the fall.

In Sanders’ case, the Vermont senator’s approval rating has been in a steady decline in the 2020 race where he has never managed to match his 2016 support when he was the sole repository for the anti-Clinton voters.

While he has tried to regain his footing in this race Sanders hasn’t been able to do it. There hasn’t been one big event that has turned the tide for Sanders. Rather, there’s been a slow erosion with formerly pro-Sanders voters becoming Warren supporters. That’s why there is a direct correlation between Sanders’ drop and Warren’s gain in the polls.

Although Warren and Harris are both on the move in the most recent polls, their approach couldn’t be more different.

Warren is methodical.

Harris is mercurial.

Warren’s climb has been slow and steady and has been built over every moment of every day, plan by plan.

Harris’ ascent has been like a rocket. Her confrontation with Biden in the first debate created the one moment everyone remembers.

On Tuesday night it will be Warren and Sanders on the debate stage together. Warren will likely make her case for the nomination by drawing a contrast with Sanders.

The two senators share many positions on policy matters. But Warren’s record of accomplishment far outstrips Sanders in her seven years in the Senate versus his 30 years in Congress. And Warren’s long list of plans to address problems voters care about, filled with voluminous details that she delivers with passion, makes the contrast all the more stark.

On Wednesday night it will be Harris and Biden on the debate stage. Harris could advance her case by once again prosecuting Biden’s record from the last 40 years, further showing that he is the antithesis of what voters are looking for in 2020.

If that happens then Biden will have to offer a much better defense than the first debate…a feat he has yet to perform in this race when his record has been questioned.

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Harris has been a heat-seeking missile in Senate hearings using her prosecutorial skills to eviscerate Trump nominees. While she used a more deft touch in the first debate with Biden, the effect was no less devastating and it could happen again in the debate this week.

On Thursday morning when the dust clears one thing will be clear: The fight for the Democratic nomination is now down to Elizabeth Warren vs. Kamala Harris.

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