"To the barricades!" declared the 36-year-old, who has a picture of the revolutionary left's icon Rosa Luxemburg tattooed on her left forearm, in a fiery speech that has racked up over 6.5 million views on TikTok.
Die Linke has been especially popular among young voters with its promise to fight for social justice, tax the rich, bring down surging rents and make public transport cheaper.
With the anti-immigration AfD polling at a record 20 percent ahead of Sunday's election, Die Linke has become a standard bearer in the pushback against the extreme right.
Founded from the ashes of communist East Germany's ruling party, it had been plagued by infighting and a damaging defection and until recently faced the threat of political oblivion.
Only weeks ago, Die Linke was polling below the five-percent threshold for reentry into parliament, but latest polls give it between seven and nine percent.
READ ALSO: The Left party election pledges foreigners in Germany should know about
It's a strong comeback for the party that was in disarray after its key figure Sahra Wagenknecht left the party early last year to found her own "left-wing conservative" movement, the BSW.
But while Die Linke has been on the up and up in recent weeks, the BSW, which also demands curbs on irregular immigration, is now hovering around the five-percent death zone and must fear for its survival.
'Anger in my belly'
Reichinnek joined Die Linke in 2015 with "anger in my belly about many social injustices", she told AFP.
The MP who spent time in Cairo during the Arab Spring protests also has an arm tattoo of a street art image showing ancient Egypt's queen Nefertiti with a gas mask.
"I really wanted to find people who saw things the same way as me, with whom I could change things together, and I found them in Die Linke," she said.
Reichinnek was relatively unknown before her blistering speech in the Bundestag against the AfD and the conservative CDU/CSU alliance.
The conservatives had breached a long-standing taboo by accepting AfD votes to push through a motion calling for an immigration crackdown.
The shattering of the anti-AfD "firewall" sparked mass street protests.
Since the fateful vote and Reichinnek's spirited response, Die Linke has seen a surge in grassroots support with membership reaching its highest point in 15 years.
In a recent mock election of under-18s, Die Linke emerged as the biggest party at 20.8 percent.
The party had already laid the groundwork with a light-hearted social media campaign centred around three of its "old comrades" aged in their 60s and 70s -- Bodo Ramelow, Dietmar Bartsch and Gregor Gysi.
Die Linke has run an "effective" campaign and set "very clear priorities", said political scientist Antonios Souris of Berlin's Free University.
Berlin student Thomas Jaeschke, 23, who has been distributing Linke flyers and putting up campaign posters, said the mood in the party was "very positive".
"At the campaign events there are really a lot of people there, some from all over Germany and a lot of newcomers," Jaeschke said.
He puts this down to a "well-communicated" campaign focused on core left-wing values such as "rent prices and redistribution of wealth", but also credited Reichinnek with "mobilising younger people in particular".
'German duty'
It's a far cry from a year ago, when Die Linke was plunged into crisis as Wagenknecht, 55, left to set up the Sahra Wagenknecht Alliance (BSW).
The new, Moscow-friendly party made a strong start, scoring 6.2 percent at EU elections last June and entering the government after two eastern regional elections.
Die Linke scored just 2.7 percent of the EU vote.
But support for BSW has waned this year as the party was hit by infighting and corruption allegations.
BSW drew the ire of many left-wingers when it also joined the AfD in voting for a drastic crackdown on immigration in parliament.
"In the end, Wagenknecht has not made the impact in the media that BSW might have hoped for," Souris said.
Berlin hairdresser Thomas Marienfeld, 43, said he voted for BSW in the EU elections but has now joined Die Linke.
Backing Wagenknecht in June was an "impulsive" decision that he regretted when he saw her party "voting with the AfD", he said.
Watching Reichinnek's speech, he said "I was 100 percent saying, 'Yes!' If the world swings to the right, then it is my German duty to go left."
By Claudia HORN and Femke COLBORNE
Comments