The White House will be looking closely at the numbers who show up for the immigration reform rally in Washington tomorrow.
The rally is expected to bring 50,000 reform advocates to the nation's Capitol right as the health care debate reaches its climax.
The two are related. Key votes from the Hispanic lobby have gone to the Obama plan as a deal for the President pushing immigration reform.
However, the White House knows the pressure from the right to stop an "amnesty" bill will be intense. That may be why the lone Republican, Sen. Lindsay Graham, is already backing off his stance in favor of a bipartisan bill.
If the crowd dips far under the 50,000 that organizers predict, expect less interest from the White House.
This week, Obama has been, for him, outspoken on reform, making it a centerpiece of his remarks at an Irish community reception on March 17, St. Patrick's night, and referring to it elsewhere.
But make no mistake: The White House is very leery on this topic, and will be looking to see solid grassroots support before proceeding, especially after the cauldron of health care.
That is why tomorrow's crowd numbers are so important. It remains to be seen if organizers can deliver.