Here’s your Tuesday morning update on the road to the Pennsylvania Primary:

* 21 days until Pennsylvania goes to the polls on April 22. Exactly three weeks from today.

* Both candidates will continue to work the Keystone State today. Sen. Hillary Clinton will be in Philadelphia this morning, where she will address the AFL-CIO Convention. This afternoon she’ll hold a town hall meeting at Wilkes College in Wilkes-Barre, followed by a rally tonight in Erie.

* Sen. Barack Obama continues his “Road to Change” bus tour. He’ll be in front of the AFL-CIO convention in Philly tomorrow. Also on Wednesday the candidate will film a session of “Hardball with Chris Matthews” at West Chester University.

* Don’t think all this hoopla has struck a nerve in Pennsylvania? Last Monday, which was the last day for would-be voters to register or change their registration, saw 33,000 first-time voters sign up as Democrats and another 46,000 voters change their designation to Democrat.

And those numbers likely will increase. County leaders are still processing voter applications that were mailed in by the March 24 deadline.