He is dropping out and resigning. Then the Democratic governor will appoint his replacement. Since that Governor his a Democrat he will be will appoint a Democrat to replace the Torch. Then that sitting democrat senator will petition the democratic court to put him on the ballot in November.
He will do so and Forrester will be running against a popular Democrat.
What this means is the Democrats are certain they can't hold the Senate without the New Jersey seat. That means the polls elsewhere look good for Republicans. If that were not the case they would not have used a sledgehammer to make the torch drop out.
The question is how will voters react to that ploy. Most likely being New Jersey they will vote for the Democrat.