By Mark Halperin, Bloomberg News (TNS)

WASHINGTON — Let’s all please stop asserting that Bernie Sanders can’t beat Hillary Clinton in the Democratic nomination race. Pundits and journalists galore have been declaring (alleged margin of error: zero) that the Vermont senator will lose to his party’s front-runner. Sure, his odds are long, but so far he’s shown substance, grit and surprising appeal. Why not let the voters decide who will accept the torch in Philadelphia next summer?

Clinton is, without doubt, still the odds-on favorite to win, with plenty of support, cash and ballast for the foreseeable future. Therefore, it is more germane to ask: What impact might Sanders have on the former secretary of state in the nomination fight? And, if Sanders doesn’t win his party’s nomination, what impact might he have overall on Clinton’s chances of becoming the next president of the United States?

Sanders’ surprising success has already influenced Clinton’s conduct and fortunes, and there is every reason to believe that he will continue to challenge her, influence her, and create significant problems for her as the race continues.

There are plenty of recent examples of underdog candidates in both parties who “couldn’t” win the nomination in the estimation of the chattering class but who nonetheless had an outsized influence on the contours and, indeed, outcome of the race. These include Rick Santorum and Newt Gingrich in 2012 against Mitt Romney; Pat Buchanan in 1992 against George H.W. Bush; and Jesse Jackson in 1988 against Michael Dukakis. Based on how things are shaping up so far, Sanders has the potential to adversely affect Clinton in numerous ways, echoing the underdogs who ran before. Romney, Bush, and Dukakis, not coincidentally, all lost the White House.

Here, then, are seven ways Sanders can weaken Clinton in the general election, perhaps fatally, even if he doesn’t manage to beat her for the nomination.

1. Pulling her to the left
Clinton has already taken various positions on economic and social issues that are clearly a reaction to the Sanders’ threat from the far left (and, to a lesser extent, to that of former Maryland Gov. Martin O’Malley, who also has been trying to outflank Clinton on the liberal side). In recent months, Clinton’s political and rhetorical message has boiled down to an Old-Democrat, big-government, Pelosi-Reid-AFL-CIO-pleasing stew that a skillful Republican nominee could exploit, shoving Clinton out of the vital political middle in the general election.

2. Exposing her biggest weaknesses
Even some of Clinton’s staunchest backers will tell you that she comes off to many voters as personally inauthentic and politically calculating, lacking a genuine, heartfelt message. Even some of Sanders’ biggest detractors will tell you that he is exactly the opposite. Sanders has become such a prodigious performer on the stump and in TV interviews in part because he gives Democrats an unvarnished and passionate view of his ideas, his soul, and himself.

Recently, at a major gathering of Iowa Democratic activists, almost every Clinton supporter I talked to expressed admiration for Sanders’ authenticity and policy agenda, and many said that if they followed their heart, they would vote for the underdog. If Clinton’s main four-point agenda sounds like it is the product of extensive research by her polling and focus-group teams, well, that is because it is. A lot of voters grasp that calculation intuitively, and find it a turnoff. Clinton’s perceived lack of personal and political sincerity may not cost her the nomination, but it won’t help her image with general-election voters already skeptical about her character and relatability.

3. Forcing her to go negative
When front-runners are threatened, their usual move is to kneecap the opponent, and before too long, Clinton may feel she has no choice but go on the attack against Sanders. Such a move might be effective, but it would hold peril. First, as Sanders himself has eschewed negative politics throughout his career, potent political martyrdom could ensue. Second, Clinton could look like a hypocrite, since she has been regularly railing against negative attacks from the GOP. Third, it could unleash even more vigorous Republican assaults, with far less concern about public or media backlash.

4. Playing a losing expectations game
Clinton faces a daunting expectations game. Even if she heads into Iowa and New Hampshire with solid polling leads, simply winning will not be enough. She has to finish far enough ahead of Sanders to prevent the press from treating a win like a loss. Between now and early February, polls will rise and fall, and what will constitute a win for Clinton will change. But rest assured the media will give her zero benefit of the doubt in this regard. Even if Clinton wins Iowa, say, 66 percent to 33 percent in an historic landslide, some news organizations would likely headline their stories “One Third of Iowa Democrats Reject Clinton.”

Clinton will thus have to spend a great deal of time and money in the two early states (which demographically and ideologically are among Sanders’ strongest), leaving her vulnerable in some of the later-voting states and hindering the timely formulation of a general-election strategy or message.

5. Beating her in early states
If Sanders continues to build his momentum and cut into Clinton’s lead, and she gets sidetracked by controversy (typically a given when a Clinton is on the ballot), it is not inconceivable that Sanders could win one or both of the two first states. That would instantly throw the party into a second-guessing panic, especially since it would be too late for another establishment candidate to get on the ballot in many of the delegate-rich states. Panic, needless to say, would not help Clinton look like a general-election juggernaut.

6. Forcing her to invest in caucus states
As a hedge against early losses, and with the memory of being outfoxed by Team Obama in 2008, Clinton’s campaign is going to pour resources into the post-Iowa caucus states, where Sanders’ grassroots enthusiasm allows him to compete fiercely. Once again, this dynamic means Clinton has to continue to take left-wing positions and to devote precious resources to targeting small numbers of activists, rather than building a general-election machine.

7. Forcing her into an extended nomination fight
If Sanders has early success, the press and the left (not to mention the GOP) will be eager to see how far he can go. That will mean the Clinton campaign will have to continue to allocate resources away from a general-election fight. The longer Sanders stays alive, the greater the aforementioned party panic would be. Bill Clinton dealt with this dynamic in 1992, when, amid scandal, he struggled to put away Paul Tsongas and Jerry Brown. As the conventional wisdom refrain declares, Hillary Clinton does not have her husband’s political skills — it would be more difficult for her to quash a widespread party freak-out. And it wasn’t easy for Bill. Recall how party leaders beseeched Lloyd Bentsen or Dick Gephardt to get in the race, despite expired filing deadlines and the hazards of a potential brokered convention. The rogue email server, the Clinton Foundation questions, and assorted other family controversies could dovetail with Sanders’ success and create a toxic and perhaps untenable situation for Hillary Clinton.

Now, of course, these are mostly speculative scenarios. But none is impossible or even improbable. All derive directly from Sanders’ manifest strengths, Clinton’s manifest weaknesses, and the dynamics and realities of the Democratic Party’s nomination process. Not long ago, few would have imagined that Sanders could have posed any sort of threat to Clinton’s political fortunes. Sanders might lose in the end, but his successes thus far and going forward make it more likely that Clinton will lose in the end too.

(c)2015 Bloomberg News. Distributed by Tribune Content Agency, LLC.

Photo: Senate Democrats via Flickr