For political strategists, the biggest question heading into Election Day has been whether Republicans can pick up the six seats needed to retake the Senate.

But looking ahead to 2016, when Republicans will face a tough Senate map of their own, the margin by which the GOP wins the Senate this fall is just as important as whether or not they win it in the first place.

Political handicappers are predicting somewhere between a four- and eight-seat gain for Republicans in November, and most see a GOP Senate takeover as the likely Election Day outcome. But there's a big difference between a six-seat pickup—which would give the GOP the narrowest of margins in the Senate—and a bigger win, with eight or more new Senate seats.

Winning more seats this year could help pad a Republican Senate majority enough that the tough 2016 map won't force them to cede control right back to the Democrats in two years, even if they lose a few seats back to Democrats that November. Furthermore, the path to a bigger majority runs through swing states like Iowa and Colorado, which will be must-win battlegrounds in the next presidential election.

"You've got to make hay while the sun shines," said GOP strategist Brad Todd, whose firm, OnMessage, works with top GOP Senate hopefuls like Tom Cotton and Cory Gardner. "This is the cycle for us to flip red states and purple states and get some margin. The next map is pretty blue."

If Democrats lose the Senate this fall, it will be in part because of the inhospitable map they face: The party is defending seven seats in states Mitt Romney won in 2012, including four incumbents. But the map looks almost equally fraught for Republicans in 2016, which party operatives readily acknowledge: The GOP must defend 24 seats, compared with just 10 for Democrats. GOP incumbents are up in five states that President Obama won twice—Florida, Iowa, Ohio, Pennsylvania, and Wisconsin—and two states Obama won once, North Carolina and Indiana.

Plus, the potential for GOP intra-party fights—Sen. Lisa Murkowski of Alaska, who lost a primary bid in 2010, could very well get a serious challenge again—and possible big retirements, like Sen. John McCain of Arizona, could put additional seats into play.

For Democrats, by contrast, Senate Majority Leader Harry Reid and Sen. Michael Bennet of Colorado are the only two incumbents who thus far look likely to have competitive races.

According to the The Cook Political Report's ratings for 2014, there are plenty of potential places where Republicans could pick up extra seats this fall: Seven Democratic-held seats are currently toss-ups, and three—Montana, South Dakota, and West Virginia—are expected Republican pickups.

A big win by the GOP would require the party to pick up most of the deep-red states with Democratic incumbents, like Alaska and Louisiana, as well as purple states that lean Democratic in presidential years. Topping that list are Colorado, Iowa, North Carolina, and even New Hampshire, perennial presidential swing states that are home to competitive races this cycle and will host Senate races next cycle as well.

Nick Ryan, an Iowa-based strategist and president of the American Future Fund, named Iowa, Colorado and New Hampshire as "stretch" states the GOP needs to win this fall in order to help pad the margins and prove that it can win outside of red states in 2016.

"Those stretch states are vital in 2014—because if you do buy into the analysis that the environment's right and you have a president that's not very popular, you have to be able to pick up some seats like this," he said. For example: "A Scott Brown victory in New Hampshire makes it possible that you could actually defend a Republican majority in 2016."

The GOP's challenge in 2016 is twofold: The party has more territory to defend, first of all, and it will have to do so with a presidential-year electorate that leans far more Democratic. The class of GOP senators up in 2016 were elected in the GOP wave of 2010—and especially in blue states, they will face a substantively different group of voters than the one that first elected them.

Perhaps at the top of that list are Pennsylvania's Pat Toomey and Wisconsin's Ron Johnson, both of whom are expected to face tough reelection races in 2016.

Toomey, the former Club for Growth president who defeated Democrat Joe Sestak by just 2 points, will face significant hurdles in a state that has voted for every Democratic presidential nominee since 1988—especially if Hillary Clinton, who won the Pennsylvania primary by 10 points in 2008 and has family ties to Scranton, is at the top of the ticket.

Still, Toomey has taken conscious steps to bolster his image as a bipartisan guy, said veteran Pennsylvania pollster Terry Madonna, and has avoided the kind of "partisan rants" and "rhetorical hyperbole" that helped bring GOP Sen. Rick Santorum to a 17-point loss in the state in 2006.

Also in question are Illinois, a typically blue state where GOP Sen. Mark Kirk won by a small margin in 2010, and Florida, where Republican Sen. Marco Rubio will either be up for reelection or could be giving up his seat in favor of a White House bid.

In New Hampshire, meanwhile, GOP Sen. Kelly Ayotte has an approval rating that sits at or above 50 percent, and she looks to be in good shape for reelection—but a challenge from current Democratic Gov. Maggie Hassan, which Granite State insiders say is likely if Hassan wins reelection this fall, would set up a race between two popular statewide pols.

Ayotte is "not a shoo-in by any means, but she's in a pretty solid position," said Andy Smith, who polls for the University of New Hampshire. "Certainly she's going to be challenged by Democrats, and it's going to be a strong challenge, but she's not in as weak a position as some other Republicans."

This article appears in the September 17, 2014 edition of NJ Daily.