IRAN'S PRESIDENTIAL ELECTION TOMORROW.

Iran will hold its presidential election tomorrow, and it looks like Mahmoud Ahmadinejad could face a struggle to stay in office. His primary challenger is Mir-Hossein Mousavi, a former prime minister whom Iran's reform movement has rallied behind. Mehdi Karroubi, another reformist, and Mohsen Rezaei, a conservative, are also in the race. Here are a few refresher pieces to remind us what's at stake:

Matthew Yglesias asks why Democrats are undermining Obama's democratic plan for Iran.

Ray Takeyh says that solving the Iran puzzle may be one of the most difficult -- and important -- tasks facing the United States.

Ezra Klein talks with John Edwards about negotiating with the Islamic republic.

And Gershom Gorenberg discusses the military tensions between Iran and Israel.

Dana will offer some reporting on the elections later in the day, so stay posted.

--Alexandra Gutierrez