The Red Devils looked to have lost their crown to Manchester City earlier in the season when they trailed their rivals by as many as seven points.
However, a recent run of positive results has seen United move to the top of the Premier League table with just four matches remaining.
United legend Charlton believes that a lot of the credit for the team's rise should go to the manager.
"So much credit has to go to Alex and his coaches for having United involved in the title race again this season," said Charlton.
"At the start of every campaign, you want to avoid injuries and suspensions, and United have had such incredible misfortune with injuries that it's really staggering to be in the position we're in.
"There's been so much said about Alex, especially this season with him passing his 25th anniversary, that it's hard to add anything new. He's just marvellous and the way he lifts everybody around him is incredible."
Next up for United is a home fixture against Everton at the weekend.