Superstar, the weekly Arabic version of UK hit Pop Idol, has been broadcast for several months on Lebanon's satellite channel Future TV, taking Jordan and several other Arab countries by storm.
But the heat soared on Monday when results for Sunday's show were announced.
Lebanese contestant Melhem Zein, who made it to the top three slots, was eliminated from the race, and Karzon was left to face Syrian amateur singer Ruweida Attiyeh.
Before leaving the stage Zein threw a bombshell when he asked television viewers across the Arab world who had supported him to back Attiyeh.
His remarks fuelled widespread rage in Jordan and triggered clashes outside Future TV's station in Beirut, when Zein's fans stormed the station protesting that his defeat was unfair.
Jordanians from all walks of life, as well as companies, state television and the press reacted by throwing their weight behind Karzon to ensure she would make it to the top in the show's final segment on Sunday.
Jordan's rival mobile phone providers - Fast Link and MobileCom - have decided to give their full support to Karzon, 19, who has won hearts across the Arab world with her magical voice, warm smile and simple demeanour.
"Give your vote to Diana for our happiness to be complete."
Both have dedicated a media campaign to her, with advertisements appearing daily in the press urging Jordanians to rally around the young singer.
The MobileCom ads shows her wearing a long traditional embroidered Jordanian dress and captions that read "A beautiful Jordanian dream" or "Give your vote to Diana for our happiness to be complete".
MobileCom executive Hazem Massarweh said the company has set aside 20,000 dinars ($35,000) for the campaign to promote Karzon "because we want to encourage our local talent".
Fast Link is also urging Jordanians, through SMS messages on their mobile phones, to vote for Karzon. It is also publishing ads in local newspapers saying, "Give your voice to the most beautiful voice".