Marco Rubio is quietly amassing organizational backing in states often ignored by presidential candidates, preparing for a Republican primary that could go long and become a knife fight for delegates.

The Florida senator's growing empire of state campaign chairmen and designated grassroots supporters stretches from Maine to Alaska, and is populated in between with volunteer teams in Connecticut, Michigan, Pennsylvania, Rhode Island, Tennessee, Vermont and Wyoming. Victory in those states could win Rubio roughly 300 delegates of the approximately 1,200 he needs to be crowned the GOP presidential nominee next July.

The Rubio campaign declined to comment for this story. But among his advisers is Rich Beeson, the Republican consultant who helped devise Mitt Romney's delegate strategy after the eventual 2012 nominee failed to close out the competition and found himself in an extended scrum with underdog Rick Santorum. Romney pulled it off with some creative moves, like focusing on winning primaries in usually forgotten U.S. territories like Guam.

"It's incredibly complicated," said Katie Packer, who served as Romney's deputy campaign manager three years ago and was involved in plotting his hunt for delegates. "It's a combination of really good ballot access lawyers making sure you're checking the boxes to get on the ballot, and people who understand — state by state — all of the delegate rules."

The foresight and resources required to compete in an extended primary battle shouldn't be underestimated, and could divide the campaigns that are, and are not, able to go the distance. Every state has different rules for candidates to qualify for the ballot, and different regulations for how delegates are allotted. Some states award delegates proportionally; others are winner-take-all. Some states hold caucuses, others traditional primaries. Some states don't automatically award delegates to the winner of the primary.

In 2012, the results of poor planning and scarce campaign cash on the part of some candidates was evident when only two GOP contenders, Romney and Ron Paul, did what was necessary to qualify for the Virginia primary. In the 2008 Democratic primary, then-Sen. Barack Obama outmaneuvered then-Sen. Hillary Clinton in the hunt for delegates, helping him win his party's presidential nomination.

Rubio is spending most of his time campaigning in the key early primary states of Iowa, New Hampshire, South Carolina and Nevada — as are most GOP contenders. It's likely that how the candidates finish in these states could significantly whittle down the field. But there are early signs that several of the candidates are positioning themselves for a long battle.

Like Rubio, Sen. Ted Cruz of Texas is building network of supporters in later-voting states, including Alabama, Arkansas, California, Georgia, Idaho, Illinois, Massachusetts, Michigan, Mississippi, New Jersey, North Carolina, Oklahoma, Virginia and Wyoming. Gov. Scott Walker of Wisconsin has campaigned in Georgia, Illinois, Missouri, Pennsylvania and Tennessee. Sen. Rand Paul of Kentucky also has expanded the scope of his campaigning, with visits to Illinois and Michigan, where Paul has a team working for him on the ground.

There are presently 16 major Republican candidates who have declared for president, with many of them eying these and other late voting states as insurance against underperforming in the first four. Success in Iowa, New Hampshire, South Carolina and Nevada is usually a prerequisite for remaining competitive going forward. But with such a large field, the possibility exists that two candidates will emerge from the fray with a legitimate chance of winning.

That would leave them in a duel for delegates either entering, or exiting, the expected super Tuesday contest of Southern states being dubbed the "SEC primary." A handful of Midwestern states with large delegate allotments, also vote around the same late winter time frame. Florida, normally a key battleground, is expected to go to either Rubio or former Florida Gov. Jeb Bush in a de facto head-to-head matchup.

Three years ago, once Romney realized he was in a dogfight with Santorum, his advisers settled on a strategy that prioritized scooping up delegates in places like American Samoa, Guam, the Northern Mariana Islands, the U.S. Virgin Islands and Puerto Rico. Romney dispatched family members to campaign in these territories ahead of their primaries, a move that helped him weather Santorum victories in states like Colorado, Missouri and Kansas, to name a few.

"There are definitely some interesting pathways out there for a few of these [2016] guys," said one Republican operative who handled delegate strategy for another 2012 candidate.

Disclosure: The author's wife works as an adviser to Scott Walker.