Another Tuesday, another critical day for the 2012 Republican presidential contenders.

This time the locations are Michigan, where most polls close at 8 p.m. ET, and Arizona, where voting ends at 9 p.m. ET. The story political junkies are watching closest: Will former Massachusetts Gov. Mitt Romney, a Michigan native, hold off a strong challenge there from former Pennsylvania Sen. Rick Santorum?

Also on the ballots, of course: former House Speaker Newt Gingrich and Rep. Ron Paul, R-Texas.

Once again, we're helping out the Elections Desk by live blogging. Starting around 7 p.m. ET, you should be able to see our latest updates right on the homefront. Join us if you'd like to follow along.

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