I'll leave the task of describing why the Iran deal should be rejected to others. Instead, I'd like to bring up the reality that unless 12 Democrats in the Senate and 43 in the House join the effort to stop the deal, even assuming that all Republicans do so, the deal will take effect. This means that Congress' time to review the deal is not rally-the-base time, it is persuade time. That is, it is time to work on persuading the necessary Democrats in the House and Senate that it would be better to continue as is with the sanctions than to allow the deal to take effect.
Unfortunately, the bluster from the Republicans will not have any persuasive power. Anything that can be dismissed as knee-jerk opposition to a deal with our enemies will not have any persuasive power. Rallying a pro-Israel Democratic constituency could have the needed persuasive power, if there is a large enough group of them willing to make the required noise. However, it is unlikely to be enough. We need to understand the 12 most conservative Senate Democrats' terms for evaluating the Iran deal and then explain it within that framework in a way that would induce them to override a veto of Congress' rejection of it. It also would not hurt if the Republicans in Congress would offer some inducements, such as removing some element from the assault on Obama's domestic agenda, in order to get the needed handful of Democrats to support the override.
Update: The Jerusalem Post has an editorial making the same point with a few details added. Some particularly sage advice:
Second, the Israeli campaign against the deal must avoid personal attacks on the US president. Lobbying efforts must focus on the issues. Democrats will rally around their president if they perceive him to be the subject of baseless ad hominem accusations.