The POTUS has no control. Congress passes a budget plan and hasnt done a balanced budget in...what, 30 some years?
Well ya, I know that. But, he does pick his team and surrounds himself with 'talent', and does have some pull doing things looking at what Mr Obama has done. To. Us.
The potus pretty much controls his party with their policies that got them elected. IE obamacare, Obama's foreign policy, Obama's closing down gitmo so they detainees can get back into the fight to kill Americans, and the list goes on.