The claim that is being made in this article is that if all the Christian in America voted, the Republican party would always win. This is false. While it is true that Christians make up a majority of America's population, back up by a pew-research study, not all Christians vote for the Republican party.
https://www.pewresearch.org/religious-landscape-study/
This can be found in another pew-research study, which is backed up by similar findings in a PRRI study.
https://www.pewresearch.org/politics/2024/04/09/party-identification-among-religious-groups-and-religiously-unaffiliated-voters/
https://www.prri.org/spotlight/religion-and-the-2024-presidential-election/
Combining the findings from another pew-research study, backed up by similar findings in a PRRI study, White Evangelicals are the group of Christians that lean the hardest to the Republican party, with 84% of them voting red, but Evangelicals are only 23% of the population.
Protestants as a whole vote red 59% of the time, and Catholics vote red 52% of the time. This is a majority, but not nearly enough for Christians alone to decide an election.