Ed Gillespie’s announcement last week that he is challenging Sen. Mark Warner (D) in Virginia is the latest piece of evidence that Republicans have learned well from the recruitment strategy of Senate Democrats in 2012.

Gillespie is not a favorite in the race. He probably has less than a 30 percent chance of winning. But he is a serious candidate who will raise money and run a real campaign against Warner. And if the national environment collapses for Democrats or the incumbent makes a major mistake, Gillespie will be positioned to win in a swing state. In short, Virginia is now a race in play — an expansion of the playing field on which the fight for the Senate majority will take place.

Republicans are up to something similar in New Hampshire, where Scott Brown, a former senator from Massachusetts, certainly seems to be moving in the direction of challenging Sen. Jeanne Shaheen (D) this fall. Say what you will about Brown — carpetbagger, lost his last election, etc. — but with him, the race is on the map, and without him it, well, isn’t.

Republicans have set a similar course in Michigan, where former secretary of state Terri Lynn Land continues to post very impressive numbers in the battle for the Democratic-leaning seat being vacated by Sen. Carl Levin (D).

The GOP’s 2014 strategy might ring a bell. That’s because it’s the exact same strategy Democrats used in 2012 to unexpectedly hold the Senate. Facing daunting raw numbers — 21 Democratic seats were up, compared with just 10 Republican ones — as well as a slew of Democratic retirements in difficult states (Wisconsin, Virginia and North Dakota), Senate Democrats did everything they could to widen the playing field.

Take Indiana and North Dakota.

In Indiana, then-Rep. Joe Donnelly (D) decided to run for the Senate in the belief that if Sen. Richard G. Lugar lost in the Republican primary, the race might be winnable. Lugar lost and Donnelly won — despite the fact that President Obama took only 44 percent of the vote in the state. In North Dakota, former state attorney general Heidi Heitkamp (D) decided to run despite the state’s Republican lean. She ran a great campaign, her heavily touted Republican opponent did not, and she now sits in the Senate.

What Republicans are trying to do is give themselves the sort of margin for error in 2014 that Democrats didn’t allow them in 2012. Let’s do the math.

Republicans need to win six Senate seats to retake the majority. In West Virginia, South Dakota and Arkansas, Republicans recruited their strongest candidate and, at worst, have even odds to take those Democratic seats. That gets the GOP halfway to its goal.

The key to the Republican strategy is making the next tier of seats (and recruits) as large as possible since a few candidates will flame out, some incumbents will prove tougher to beat than they appear, and the national political environment could shift several times between now and November.

By our count, Republicans are aiming for seven Democratic seats in this second tier: in Alaska, Louisiana, Michigan, Montana, New Hampshire, North Carolina and Virginia. (Some Republicans would throw Minnesota into that mix because of self-funder Mike McFadden’s candidacy, but we remain skeptical.) In some of those states, Republicans have solid candidates in primary fights (Alaska with Dan Sullivan, Louisiana with Bill Cassidy). In others they have unproven fields (North Carolina, Montana, Michigan). In still others, it remains to be seen whether the Democratic incumbents are genuinely vulnerable (New Hampshire, Virginia).

But in all cases, there is a credible Republican in the race who can raise the money needed to compete against the incumbent and who has a real chance at being the party’s nominee. That means Republicans need to win only three of these seven second-tier races — assuming they take Arkansas, South Dakota and West Virginia, and don’t lose their own seats in Kentucky and Georgia — to retake the majority.

At the moment, Senate Republicans have two major holes in their “expand the map” strategy: Colorado and Iowa.

Colorado has moved toward Democrats in the past two presidential elections but remains a place where Republicans need to be able to compete. The GOP field is currently led by Ken Buck, who is best known for losing a very winnable race for Senate in 2010.

In Iowa, the retirement of Sen. Tom Harkin (D) should have made for a sterling pickup opportunity for Republicans, but their field, at least at the moment, is a mishmash of sort-of-knowns and unknowns.

Keep an eye on those two states over the next few months. (The filing deadline in Iowa is March 14; in Colorado, it’s March 31.) Adding one of those two — or maybe even Minnesota making it into that second tier — would further expand Republicans’ paths to a majority.

One thing’s for sure: If they make it over the top this November, Senate Republicans should send their Democratic counterparts a nice thank you gift for showing them the way.