March is shaping up to be a crucial month in the 2013 campaign. A great deal will be sorted out in the next 23 days, and we should have a clearer view of the state of play in some of the year's biggest races by month's end. Consider:

* This is the month that Lt. Gov. Bill Bolling (R) will announce whether or not he will run as an independent for governor of Virginia. His decision will have an enormous impact on the race.

Will Virignia Lt. Gov. Bill Bolling (R) run for governor as an independent? ((Tracy A. Woodward/The Washington Post) Will Virignia Lt. Gov. Bill Bolling (R) run for governor as an independent? ((Tracy A. Woodward/The Washington Post)

* Voters in South Carolina's 1st district will nominate candidates for the special election there. The dream matchup between former governor Mark Sanford (R) and Elizabeth Colbert Busch (D) seems like a good bet. But we won't know for sure until the March 19 primary -- which could run into overtime, if candidates don't claim majority support.

* In Massachusetts, if Rep. Stephen Lynch hasn't made at least some dent in Rep. Ed Markey's lead in the race for the Democratic nomination by the end of this month, he will have only four weeks left to make up ground on the frontrunner, with an April 30 primary looming. And if Markey expands his lead, he could make it nearly impossible for Lynch to catch up.

So spring forward this weekend into Daylight Savings Time, as well as into one of the most decisive political periods of the year!

And now, to the Line! Below we rank the top five races of 2013. The marquee matchup with the most at stake is number one.

5. South Carolina 1st district special election (Republican-held): Colbert Busch, better known as Stephen Colbert’s big sister “Lulu,” is out with her first ad – a pretty standard-issue bio ad. As The Fix has argued before, Colbert Busch will be a distinct underdog, no matter which of the myriad Republicans in the race she faces, but Democrats think she would have a decent chance against scandal-tarred Sanford. Special elections are indeed unpredictable enough that she could win in a district that went 58 percent for Mitt Romney last year, but we would hardly expect it. (Previous ranking: N/A)

4. Los Angeles mayor (Democratic-held): The May 21 runoff election will produce a first, no matter who wins. If City Controller Wendy Greuel wins, she will become the city's first ever woman mayor. If City Councilman Eric Garcetti wins, it will mark the first time Los Angeles has elected a Jewish mayor. Neither candidate secured a majority in Tuesday's low-turnout election, prompting the spring runoff. Garcetti runs well among Hispanic voters while Greuel's strength is her labor backing. The race could come down to which candidate does a better job wooing supporters of the six candidates who didn't make the runoff. Greuel is viewed as a bit more moderate, something that could give her a leg up in consolidating support from more conservative voters. The race is technically nonpartisan, but both Greuel and Garcetti identify as Democrats. (Previous ranking: 5)

3. Massachusetts Senate special election (D): So far, so good for Markey, Senate Democrats' preferred candidate. A poll released earlier this week showed him up double-digits against both Lynch and the entire Republican field. Still, nearly a quarter of the Democratic primary electorate remains undecided, suggesting that Markey shouldn't count his chips just yet. We've seen a Massachusetts special election take an unpredictable turn before. Democrats are determined not to let it happen again. (Previous ranking: 3)

2. New York City mayor (independent-held): New York City Council Speaker Christine Quinn remains the favorite for the Democratic nomination – which is likely to determine the next mayor. A recent Quinnipiac University poll showed her leading Public Advocate Bill de Blasio 37 percent to 14 percent, with former city comptroller (and 2009 Democratic nominee) William Thompson at 11 percent and current Comptroller John Liu at 9 percent. If Quinn can get to 40 percent, she would avoid a runoff. If she can’t hit that number, it’s a new ball game. The primary is apparently set for September, after the state legislature rebuffed an attempt to move it to June. (Previous ranking: 2)

1. Virginia governor (R): The big question these days is whether Bolling launches a potentially game-changing independent bid. The bigger question is whom it would hurt more: state Attorney General Ken Cuccinelli II (R) or former DNC chairman Terry McAuliffe (D). Bolling is a Republican, but both declared candidates have plenty for independents not to like, which could make Bolling a formidable middle-of-the-road candidate. And polls suggest both would cede similar numbers of votes. Bolling will announce his decision by March 14. (Previous ranking: 1)