Fox News:

While Donald Trump still holds a wide delegate lead in the GOP presidential primary race, his Achilles heel has been a perceived weakness in his ground game. Seeking to capitalize on this, Cruz has outmaneuvered Trump lately in the behind-the-scenes battle for delegates in places that don't assign them through traditional primaries or caucuses.

Enter states like North Dakota, and now Colorado.

Both eschewed traditional primary elections and instead held conventions -- where delegates not necessarily bound to any candidate are selected. Cruz saw this as an opportunity anyway to get allies elected to the slate, banking on their support in the event of an open convention.

The candidate, after picking up more likely delegate allies than Trump in last weekend's North Dakota convention, has been on a roll in Colorado.

Thirty-four delegates are at stake in the convention process, and the Cruz campaign told Fox News on Friday afternoon it has picked up 15 delegates so far in a series of local GOP meetings. The process culminates Saturday at the state convention where a final 13 delegates will be selected.

In Colorado, delegates can pledge themselves to a candidate or run unbound. Those who do pledge only do so for the first round of voting at the convention in Cleveland. The Cruz campaign says the pro-Cruz delegates selected so far are a mix of pledged and unbound but say they will back Cruz in Cleveland.

“His team has been masterful in being able to use their influence and power … to pull the delegates in,” Jeanne Zaino, professor of political science and international studies at Iona College, told FoxNews.com LIVE.

Trump has been trying to beef up his team's delegate expertise, recently hiring convention veteran Paul Manafort to organize and implement his convention push.