State: Ohio
Type of election: Primary
How it works: 63 delegates are at stake. 48 delegates are awarded in winner-take-all congressional districts. Santorum submitted only a partial slate of delegates by the deadline. If he wins in those districts, he can only be awarded only the number of delegates he submitted. The remaining delegates will be designated unbound until a three-member panel from the Republican party's central committee decides who the delegates will be appointed by. The remaining 15 delegates will be allocated to any candidate who gets a majority of the statewide vote or distributed proportionately among any candidates who get at least 20 percent of the vote.
Official election results: Ohio Secretary of State
Republican candidates: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum (all others have dropped out or are polling at less than 1 percent)
Democratic candidates: There is no Democratic presidential primary.
Previous performance: In 2008, Romney dropped out prior to the primary, but still received 5 percent of the vote and finished fourth. Paul finished third with slightly fewer votes. Obama finished second with 45 percent of the vote.
Newspapers: Cincinnati Enquirer, Cleveland Plain Dealer, Columbus Dispatch, Toledo Blade, full list
Television stations: Full list
Progressive blogs: Buckeye State Blog, Ohio Daily Blog, Plunderbund
Latest polling: New York Times:
Nate Silver gives Romney a 65 percent chance of winning, while Santorum gets a 35 percent chance.
Bottom line: This appears to be closer than Silver suggests (although he's been right on the money so far) and this could be the biggest battleground and the biggest competitive prize of the day.
State: Oklahoma
Type of election: Primary
How it works: 40 delegates are at stake. 15 delegates are chosen by congressional district with a majority winner getting three delegates and the delegates being distributed to as many as the three top vote-getters as long as they are above 15 percent of the vote. 25 delegates are given to a statewide majority winner or distributed proportionately to candidates getting at least 15 percent.
Official election results: Oklahoma State Election Board
Republican candidates: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum (all others have dropped out or are polling at less than 1 percent)
Democratic candidates: Barack Obama and minor candidates.
Previous performance: In 2008, Romney finished third with 25 percent of the vote. Paul finished fourth with just over 3 percent. Obama finished second with 31 percent.
Newspapers: The Oklahoman, Tulsa World, full list
Television stations: Full list
Progressive blogs: Blue Oklahoma
Latest polling: New York Times:
Nate Silver gives Santorum a 91 percent a chance of winning, Romney an 8 percent chance and Gingrich 1 percent.
Bottom line: A bit more conservative state than the rest looks to go for Santorum, which shouldn't be a surprise. Santorum's challenge is to win in a more moderate state.
State: Tennessee
Type of election: Primary
How it works: 55 delegates are at stake. 27 delegates are awarded by district. If a candidate gets two-thirds of the vote in a district, they winn all three delegates. Otherwise the top two candidates in the district split the vote 2-1. The remaining delegates are given to the candidate who gets at least two-thirds of the statewide vote or given proportionately to candidates who get at least 20 percent of the vote.
Official election results: Tennessee Secretary of State
Republican candidates: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum (all others have dropped out or are polling at less than 1 percent)
Democratic candidates: There is no Democratic presidential primary.
Previous performance: In 2008, Romney finished third to Huckabee with 24 percent of the vote, Paul finished fourth with over 5.5 percent. Obama finished second in the Democratic primary with just under 40.5 percent.
Newspapers: Nashville Tennessean, Knoxville News Sentinel, full list
Television stations: Full list
Progressive blogs: KnoxViews, Southern Beale, Tennesse Guerilla Women
Latest polling: New York Times:
Nate Silver gives Santorum a 56 percent chance of winning, Romney a 39 percent chance and Gingrich 5 percent.
Bottom line: Santorum looks to win a Southern state, but Romney looks surprisingly strong. Gingrich is doing better in the South as well, but only looks to play a spoiler.
State: Vermont
Type of election: Primary
How it works: 17 delegates are at stake. Three are super delegates bound by the primary results on a winner-take-all basis. The remaining delegates are awarded to a majority winner or distributed proportionately among any candidate who gets at least 20 percent.
Official election results: Vermont Secretary of State
Republican candidates: Newt Gingrich, Ron Paul, Mitt Romney and Rick Santorum (all others have dropped out or are polling at less than 1 percent)
Democratic candidates: There is no Democratic presidential primary.
Previous performance: In 2008, Romney had dropped out of the race before the primary, but still got under 4.5 percent. Paul finished third with over 6.5 percent. Obama won the Democratic primary with 59 percent.
Newspapers: Burlington Free Press, full list
Television stations: Full list
Progressive blogs: Green Mountain Daily
Latest polling: Little polling has been done in Vermont.
Nate Silver gives the state easily to Romney, with Paul doing second best.
Bottom line: Romney should win easily and net a few more delegates over his rivals.
State: Virginia
Type of election: Primary
How it works: 46 delegates are at stake. 33 are awarded in a winner-take-all fashion in each congressional district. The rest are given to a statewide majority winner or given proportionately if no one wins a majority.
Official election results: Virginia State Board of Elections
Republican candidates: Ron Paul and Mitt Romney. The other candidates did not qualify because of stricter ballot rules.
Democratic candidates: There is no Democratic presidential primary.
Previous performance: In 2008, Romney had dropped out, but got over 3.5 percent. Paul finished third with 4.5 percent. Obama won the primary with nearly 64 percent.
Newspapers: Virginian-Pilot, Richmond Times-Dispatch, full list
Television stations: Full list
Progressive blogs: Blue Virginia, Not Larry Sabato
Latest polling: New York Times:
Nate Silver gives Romney a 100 percent chance of winning.
Bottom line: Without Santorum or Gingrich on the ballot, this one doesn't really count towards anything other than the delegate count. It could be a sign of the superior organization of the Romney campaign, though.