A stroke of unusual luck is giving shareholders of Freeport-McMoRan (FCX) a 26 percent return in just one week. After twelve straight days of gains in copper, the metal is now at a 15-month high. Sentiment and timing are helping the metal. If the momentum continues, FCX may touch $15 or even $20 next.Copper prices rose to $5,443 per ton at one point. Last Wednesday, November 9, the metal rose 3.4% following the Republican win in both houses of Congress. If the party’s platform is carried out in 2017, stimulus for building projects will lead to higher copper demand. This scenario is not assured and investors are ignoring Freeport’s massive debt.FCX has a debt/equity of 4.01x. The company has the option of selling down more assets to par debt. Higher construction, tax cuts, and more consumer sending will spur inflation. This would force the Fed to finally raise rates, putting pressure on FCX’s debt costs. Still, copper prices matter most right now.Related: BHP and Rio Tinto. BHP recently cut copper output.Bears hold a 9.27% short float against Freeport. The recent rally may be a short squeeze that will drive the share price higher. If copper prices hold on to their gains, this may very well play out this way. FCX will move next towards $15 - $20 per share.