Democratic voters have told us for months that beating President Trump is the most important issue for them in choosing a nominee. The best way for a candidate to show that they are a winner is by winning. And, Bernie Sanders has been winning.

While many have questioned the role that Iowa and New Hampshire should/do play in the process, the reality is that Sanders' success (and Joe Biden's flops), in these first-in-the-nation states has mattered. A lot. The three most recent national polls — ABC/Washington Post, NPR/Marist/NewsHour and NBC/Wall Street Journal — all show Sanders on top of the Democratic field by 12 to 15 points. Sanders is also surging in Super Tuesday states like California (a new PPIC poll has him at 32 percent, 18 points ahead of Biden), and Virginia (a new Monmouth poll shows Sanders tied with Bloomberg at 22 percent with Biden at 18 percent.)

Technically, Pete Buttigieg has been winning too. He currently holds the most delegates — 22 to Sanders' 21. But, that success has done nothing to boost his numbers. He's in the single digits in both the ABC and NPR/Marist polls and is in fifth place with 13 percent in the NBC/Wall Street Journal survey. Why didn't he get that post-Iowa/New Hampshire bounce? Blame Bloomberg. Instead of focusing on Buttigieg's success in those two early states, the media narrative turned to Bloomberg and his profligate spending on advertising. Bloomberg's flood of paid media injected him into the conversation among 'regular' voters as well. Since Iowa, Bloomberg has seen his support jump 7 points in the FiveThirtyEight National polling average, while Buttigieg's vote share has gone up just 3.5 points. 

Given Bloomberg's status as a top-tier contender, it was not surprising to see the other five candidates attack the former New York City mayor at the Wednesday night debate in Las Vegas. But, Sanders left the debate stage relatively unscathed. Sen. Elizabeth Warren had the best debate performance of the night - and perhaps the entire primary. But, in training her fire exclusively at Bloomberg, Warren failed to distinguish herself from Sanders, the candidate most responsible for taking her one-time frontrunner status. 

The results of Nevada and South Carolina may change the dynamics but by how much? Sanders is expected to win in Nevada. And, South Carolina is looking less like a firewall for Biden than a lifeline that's been thrown out too-late.

Another important factor working in Sanders' favor is the fact that so many of the Super Tuesday states have already begun voting. Texas, with 228 delegates at stake, started early voting on February 18th. California (with its 415 delegates) has been voting since right after Iowa. Other big states that have begun early vote include North Carolina (110) and Tennessee (64). Colorado (67 delegates) votes almost entirely by mail and those ballots have already gone out. According to Elaine Kamarck, senior fellow at the Brookings Institution and author of "Primary Politics: Everything You Need to Know about How America Nominates Its Presidential Candidates," there is no precedent for this many delegate-rich states with robust early voting programs to be voting this early in the primary process. 

Paul Mitchell, Vice President of Political Data Inc, owner of Redistricting Partners, tracks the early vote in California. As of Wednesday, more than 1 million votes had already been cast. "The big deal is that these million early voters won't have had the benefit of seeing who drops out or who makes a big flub or who wins Nevada or South Carolina, etc…" Mitchell told me.  "The way I've been phrasing it is someone might think they can dive into California after South Carolina, but it could be a very shallow pool after upwards of 40-45% of the state's Democratic Primary voters have already returned their ballots. We will see what happens, but if Biden wins South Carolina, it is probably happening too late to impact California."

Mitchell also told me that the Sanders campaign, perhaps having learned the ways of California's primary voting behavior from their loss in the state in 2016, has put together a robust early vote effort. 

In Texas, only Sanders and Bloomberg have been up on TV in the state.

Combine Sanders' Iowa/New Hampshire bump, with his institutional advantage in some of the Super Tuesday states, and the Vermont Senator well-positioned for a very good Super Tuesday showing. 

CNN's Harry Enten tweeted the other day that "Sanders, at this point, looks to be on track to get something like ~40%+ of the delegates on Super Tuesday... unless something shifts." FiveThirtyEight's Nate Silver has a similar projection, with Sanders at 41 percent of delegates post-Super Tuesday. And, Silver and Enten aren't alone in that thinking. On Wednesday, the Bloomberg campaign sent out a "State of the Race Memo" that warned that "Sanders is poised to leave Super Tuesday with an over 400 delegate lead versus his next closest competitor (Bloomberg), a likely insurmountable challenge." 

The Bloomberg campaign models predict Sanders coming out of March 3rd with 720 delegates to Bloomberg's 316. Biden would be in third place with 211 delegates. If, however, you add up the number of delegates projected to be won by all of the non-Bernie candidates in the primary, Sanders would have a much smaller 720 to 618 lead. The solution, argues the Bloomberg team, is for Biden, Buttigieg and Klobuchar to drop out and unite behind the former New York City Mayor. If they remain in the race, "despite having no path to appreciably collecting delegates on Super Tuesday (and beyond), they will propel Sanders to a seemingly insurmountable delegate lead by siphoning votes away from Michael Bloomberg with no upside for themselves." Nate Silver's model shows a much closer delegate race between Biden and Bloomberg, with Biden projected to net 270 delegates to Bloomberg's 273.

Even before Wednesday night's debate, it was all but impossible to believe that any candidate — especially Biden, who has staked his entire campaign on a strong showing in South Carolina — was going to drop out before the Palmetto state votes on February 29th. After Bloomberg's shaky performance in last night's debate, that incentive has dwindled to about zero.

Ultimately, however, the biggest challenge for the non-Sanders candidates has been to convince Democratic voters that Sanders is 'un-electable' in the fall. For one, as I noted above, he's been winning. It's hard to convince people that the guy who is winning elections, is in fact, unable to win an election in the fall. 

The most recent ABC News/Washington Post poll bears this out. For the first time, Sanders leads on the question of which Democrat has the best chance to defeat Donald Trump. In fact, since late January, Sanders' has seen his "electability" jump 12 points (from 18 percent to 30 percent), while Biden, who once had a commanding lead on this question, has dropped almost 20 points to just 18 percent. Bloomberg is at 17 percent. To be sure, 30 percent isn't all that impressive. But, it does show that even just one narrow win and one narrow loss have helped to move Sanders up quite a bit. What happens if he wins even more contests?

It's also hard for Sanders' opponents to call him 'out of step' with the views and values of the Democratic party. A late January survey of Democratic primary voters by Pew Research found that "while Democrats are divided over who should be the party's nominee, they share similar attitudes on a wide range of political values and on many specific issues." Even where there are differences, "[i]n some cases, these differences are a matter of degree rather than kind. For example, most Democratic voters, regardless of which candidate they prefer, support making tuition-free at all public universities and building a single government healthcare program known as "Medicare for all," which would replace private insurance. Yet only among Warren and Sanders supporters do majorities strongly support these ideas." In other words, Sanders may be more liberal than a lot of Democratic primary voters, but the issues he promotes are popular overall. 

All eyes are on Nevada this week, but unless Sanders loses on Saturday, the caucus results won't change the current trajectory of this race. Sanders is the frontrunner, and time is running out for another candidate to surpass him. Sanders may not be able to get 50 percent of all delegates by the time the primary process ends in June. But if Sanders has a big enough plurality of delegates and votes, it's going to be hard to see him lose the nomination at a 'contested convention'. At a time when party activists and voters are calling for more transparency, explaining why the guy with the most votes isn't the guy who gets the nomination is going to be a tough sell. 

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