Bernie Sanders, the inde­pen­dent demo­c­ra­t­ic social­ist sen­a­tor from Ver­mont, is run­ning for president.

With Sanders' entry into the race, the Democratic field is likely to be the most left-wing in modern American history.

In an inter­view with CBS This Morn­ing on Tues­day, Sanders told co-host John Dick­er­son that he planned to launch a mas­sive grass­roots effort to trans­form ​“the eco­nom­ic and polit­i­cal life of this coun­try,” adding: ​“We’re gonna win.”

Unlike his last run in 2016, how­ev­er, this time Sanders will join a large field of Demo­c­ra­t­ic can­di­dates who have expressed sup­port for a suite of his sig­na­ture poli­cies: Medicare for All, tuition-free col­lege, cam­paign finance reform and tax­ing the wealthy to improve the lot of the mid­dle and work­ing class­es. Since 2016, the polit­i­cal grav­i­ty in the Demo­c­ra­t­ic Par­ty has shift­ed toward Sanders to an astound­ing degree. With his entry into the race, the Demo­c­ra­t­ic field is like­ly to be the most left-wing in mod­ern Amer­i­can history.

How did this hap­pen? How did the Demo­c­ra­t­ic Party’s long, timid hang­over from Rea­gan­ism sud­den­ly end? How did Sanders, long a polit­i­cal odd­i­ty in DC — a self-described social­ist through­out the Cold War years, who vis­it­ed the Sovi­et Union for his hon­ey­moon in 1988; who resist­ed the call of Clin­tonite tri­an­gu­la­tion; who railed against eco­nom­ic inequal­i­ty when most Democ­rats were cozy­ing up to big busi­ness — man­age to realign the Demo­c­ra­t­ic solar sys­tem around his set of solid­ly left-wing policies?

A com­mon mis­con­cep­tion about Sanders’ 2016 cam­paign was that he ​“promised” a polit­i­cal rev­o­lu­tion — a wave of civic action that would sweep away the forces of reac­tion and their bil­lion­aire back­ers in DC, inau­gu­rat­ing a new era of egal­i­tar­i­an pol­i­cy­mak­ing. But Bernie’s ​“polit­i­cal rev­o­lu­tion” was nev­er a promise, it was a plea.

Bernie was end­less­ly crit­i­cized for over-promis­ing dur­ing his cam­paign, ignor­ing the prag­mat­ic pol­i­cy ques­tions in favor of attrac­tive rhetoric. ​“You have peo­ple, I believe, who do not under­stand how hard it is to make change,” then Sen. Bar­ney Frank (D‑Mass.) said of Sanders sup­port­ers in April 2016, ​“the impor­tance of not just being ide­al­is­tic, but being sen­si­bly prag­mat­ic and keep­ing their ideals.”

But con­trary to the per­cep­tion of his cen­trist crit­ics, the Sanders cam­paign was the most hon­est in recent mem­o­ry. Hillary Clinton’s more incre­men­tal demands were no more pos­si­ble in a GOP-con­trolled Con­gress than Sanders’ more ambi­tious agen­da. What Sanders told his sup­port­ers was the truth: With­out a whole­sale reorder­ing of the polit­i­cal sta­tus quo — only pos­si­ble when mas­sive num­bers of pre­vi­ous­ly unen­gaged peo­ple take to the streets, the polls and the pick­et lines — noth­ing in his agen­da could be achieved.

In oth­er words, if you want sub­stan­tive pro­gres­sive change, but believe we can get there with­out a mas­sive social move­ment, you are the idealist.

This was the les­son of Sanders’ 2016 cam­paign, one the young crop of new pro­gres­sive Democ­rats in Con­gress led by Alexan­dria Oca­sio-Cortez, Ilhan Omar and Rashi­da Tlaib has learned. Inso­far as ​“prag­ma­tism” is about effi­ca­cy, some­times offer­ing an uncom­pro­mis­ing vision — one which inspires mass par­tic­i­pa­tion and grass­roots move­ment ener­gy — is the prag­mat­ic approach. Like­wise, in a pop­ulist moment, noth­ing is less prag­mat­ic than an explic­it appeal to pragmatism.

Of course, Sanders did none of this by him­self. Left elec­toral strate­gists (and vot­ers) were look­ing for a can­di­date to con­test Hillary Clinton’s coro­na­tion, if only to push her to the left and intro­duce some pro­gres­sive pol­i­cy ideas to the pub­lic. Many of them hoped Eliz­a­beth War­ren would run. When War­ren declined, the orga­niz­ers of the ​“Draft War­ren” cam­paign grav­i­tat­ed toward Sanders instead. These orga­niz­ers employed a ​“dis­trib­uted orga­niz­ing” mod­el which allowed local activists to par­tic­i­pate semi-autonomous­ly in build­ing the Sanders cam­paign — through social media and in the streets — giv­ing elec­toral work the feel (and effect) of a mass movement.

Mean­while, it’s dif­fi­cult to dis­tin­guish between the forces that Sanders gen­er­at­ed and those that he effec­tive­ly har­nessed. As evi­denced by the suc­cess of Don­ald Trump’s pop­ulist appeal — pho­ny as it may be — and the rise of anti-elite sen­ti­ment world­wide, the set­tled neolib­er­al order is expe­ri­enc­ing a glob­al cri­sis of legitimacy.

Polit­i­cal sci­en­tists use the term ​“align­ments” to describe dis­crete eras of hege­mon­ic rule by one set of polit­i­cal forces and ideas. (“Hege­mo­ny” — an academic’s word that aspir­ing pop­ulists should avoid like the plague — sim­ply means hav­ing suf­fi­cient pow­er in soci­ety to define the dom­i­nant com­mon sense.) Every align­ment is upheld by a set of ideas which jus­ti­fy the dom­i­na­tion of one con­stituen­cy over others.

Dur­ing the Rea­gan align­ment (which oth­ers call ​“neolib­er­al­ism” or, in Britain, Thatch­erism), politi­cians across the spec­trum treat­ed as com­mon sense the idea that a ​“ris­ing tide lifts all boats,” that GDP was the only rel­e­vant mea­sure of social health, and that those unable to thrive in a glob­al econ­o­my do so out of lazi­ness or some oth­er moral flaw.

Since he began his polit­i­cal career in the 1970s, Sanders has been offer­ing a decid­ed­ly alter­na­tive vision, root­ed in con­fronting con­cen­trat­ed eco­nom­ic pow­er through grass­roots activism. His anti-plu­to­crat­ic ideas are res­onat­ing with Amer­i­cans today — espe­cial­ly younger and more diverse Amer­i­cans — because the era in which mar­ket fun­da­men­tal­ism and unfet­tered finance under­gird the polit­i­cal con­sen­sus is final­ly over.

When the legit­i­mat­ing ideas of an exist­ing polit­i­cal align­ment stop mak­ing sense, it sig­nals the end of that align­ment. The legit­i­ma­cy of the exist­ing elite is imper­iled — and there opens a pos­si­bil­i­ty to artic­u­late a new com­mon sense.

Sanders was mere­ly the first major politi­cian on the Left to give voice to this pro­gres­sive alter­na­tive when Amer­i­cans were ready to hear it. Democ­rats who have already entered the 2020 pri­ma­ry are fol­low­ing his lead. War­ren has pro­posed a 2 per­cent wealth tax on the ​“ultra-wealthy,” while Sen. Kirsten Gilli­brand has cham­pi­oned a finan­cial trans­ac­tion tax. Sen. Kamala Har­ris has endorsed Ocasio-Cortez’s call for a Green New Deal to com­bat cli­mate change. This is realign­ment in action.

Despite what some pun­dits have said, Sanders’ entry into the pres­i­den­tial pri­ma­ry fray doesn’t auger a replay of the 2016 pri­ma­ry. The polit­i­cal ground has shift­ed beneath our feet. The con­test between ​“prag­mat­ic” sup­port­ers of Clin­ton and ​“ide­al­is­tic” sup­port­ers of Sanders is over. The nar­ra­tive nev­er made sense in the first place. Whether or not Bernie Sanders wins the Demo­c­ra­t­ic nom­i­na­tion in 2020, his vision has already rede­fined its horizons.