Since the June 26-27 Democratic presidential debates, the candidate rankings have shifted and it now appears the Democratic nomination is up for grabs. The winner will be determined by voters perception of which candidate is most electable.

A June Gallup report found that "58 percent of Democrats and Democratic-leaning independents prioritize a candidate's ability to beat Trump over their views on important issues." (This finding held across all demographic groups except for younger voters—aged 18 to 29.) Gallup concluded: "The diverse field of Democratic presidential candidates would be well-advised to focus their debate performances and campaign strategies on looking like they can beat Trump instead of worrying about highlighting their issues positions" (emphasis added).

What does it mean to "[look] like they can beat Trump"? Depending upon the Democratic voter, being electable means that their candidate adopts a particular stance/attitude. During the debates we saw four different approaches.

1. Some folks want a candidate who will be "tough" enough to stand up to Trump. Trump's a liar and a bully and these voters want a candidate who can call him out.
2. Others want a Democratic candidate who can talk to the "blue-collar Obama voters" who, in 2016, voted for Trump. On the first night of the Democratic debate, Congressman Tim Ryan referred to these voters: "[The Democratic Party is] not connecting to the working class people in the very states that I represent in Ohio, in the industrial Midwest... We have got to change the center of gravity of the Democratic Party from being coastal [and elitist]... to get those workers back on our side." This is the political stance: "I feel your pain."
3. Some Democrats want a candidate who can beat Trump on specific issues such as healthcare, immigration, climate change, gun control, and housing, among others. This is a more intellectual stance: America has problems but Trump is a dummy who offers no real solutions, whereas the Democratic candidate does.
4. Finally, there are voters who want to take on Trump's immorality. New York Times opinion writer David Brooks is in this category. In his June 25th column, Brooks wrote: "A decent society rests on a bed of manners, habits, traditions, and institutions. Trump is a disrupter. He rips to shreds the codes of politeness, decency, honesty, and fidelity, and so renders society a savage world of dog eat dog." These voters want a candidate who emphasizes that Trump is immoral; whereas, the Democratic candidate can be trusted.

The top-four Democratic candidates—Joe Biden, Bernie Sanders, Elizabeth Warren, and Kamala Harris—offer different perspectives on what it means to be electable. Former Vice President Biden seems to have staked his electability claim on (4) and (2). Biden introduced his campaign in a video where he spoke about the August 2017 white-supremacist Charlottesville rally: "I believe history will look back on four years of this president and all he embraces as an aberrant moment in time. But if we give Donald Trump eight years in the White House, he will forever and fundamentally alter the character of this nation, who we are. And I cannot stand by and watch that happen." Biden plans to seize the moral high ground. In addition, Biden has spent a lot of time in Pennsylvania and the industrial Midwest, talking to voters in traditionally Democratic areas that voted for Trump.

Biden talks tough. He assures voters that he can stand up to Trump. But that's not his strong suit. Nor is policy. Biden is running as a nice guy who can bring us together.

The champion of the intellectual approach (3) is Elizabeth Warren. ("I have a plan for that.") For voters who want a candidate who can out-wonk Trump on any of the important policy issue, it's hard to ignore Sen. Warren. In the last couple of months, she's gained a lot of support because of her thoughtful plans.

There's no doubt that Democratic voters will think Warren is smarter than Trump. Her electability problem is that many Democrats may not believe she can stand up to America's biggest bully.

In 2015-16, the wonk candidate was Bernie Sanders. Now it appears that Elizabeth Warren has seized this mantle. Recently she's gained support, at the expense of Sen. Sanders.

There's no doubt that Sanders can stand up to Trump. But Bernie's style turns off many women.

The remaining top-tier Democratic candidate is Sen. Kamala Harris. For many Democrats, Harris comes across as the best prospect for standing up to Trump, calling him out as a bully (1). ("We have a predator living in the White House.") Harris can be a commanding figure. In the Senate, Harris showed this with her interrogations of Brett Kavanaugh, Jeff Sessions, and Bill Barr. During night two of the first Democratic candidates debate, Harris took control about twenty minutes in. There was cross-talk between the candidates and Sen. Harris put up her hands in a calming motion and said: "Hey, guys, you know what? America does not want to witness a food fight, they want to know how we are going to put food on their table." From that point on, Harris commanded the debate.

The latest Quinnipiac poll of Democratic voters shows Biden in the lead (22 percent), Harris close behind (20 percent), with Warren garnering 14 percent, and Sanders 13 percent. (All the other candidates had single digit support.) Since the previous April Quinnipiac poll, Harris and Warren gained voters at the expense of Biden and Sanders. In April, Biden had a commanding lead over Harris in two categories: women and black voters. Now, Harris has taken the lead with women and she's cut Biden's margin among black voters from 31 percentage points to only 4.

The gains for Sen. Harris are particularly impressive when you consider that one-third of Democratic voters either haven't heard about her or know so little they have no opinion.

There's a long way to go before the February Iowa caucuses but, at the moment, Kamala Harris is surging because many voters are taken with her commanding presence and, for this reason, believe she has the best chance of beating Trump.