They had probably bought most of the country's media because they kept reporting on her good deeds.
One could say the two most famous women in Hwa Xia were Xinghe and Tong Liang. When the rumors of presidential election started flying, some said Tong Liang was planning to join the running and that gained quite a lot of support from the public. In today's day and age, an election was nothing more than a popularity contest; the more famous candidate would most likely win. No one really cared about the candidate's background or qualifications. As long as one had made a name for oneself, either through scandal or bright results in a field remotely related to politics, one would have a valid voter base.
Therefore, even without the announcement, the support for Tong Liang was already sky high. It was like the whole country was hoping she would become the President.
This phenomenon only confirmed Madam President and Elder Shen's suspicion regarding the Tong family!